[A] classified [B] conclusion [C] discovered [D] exactly [E] existing

[F] immediately [G] inferior [H] massive [I] misidentified [J] prior

[K] question [L] remains [M] species [N] specimens [O] spot

The megalodon may have been a giant predatory sea creature measuring as much as 50 feet, but scientists believe it was no match for the competition posed by the great white shark—who they think wiped it out.

An international team of paleontologists (古生物學(xué)家) arrived at this【C1】_____as they tried to answer when the Otodus megalodon went extinct. They think the biggest ever shark was likely killed off at least a million years 【C2】__to current estimates. To calculate when the【C3】__sea creatures were last seen in Earth’s oceans, the researchers studied every megalodon fossil【C4】__in California and Baja California, Mexico, where the【C5】__of these fish are plentiful. They also studied【C6】_____data on fossils, and found inaccuracies. The results led the researchers to think that the megalodon went extinct much earlier than previously thought.

This calls into【C7】_____past research that suggested the great white shark’s hulking cousin went extinct around 2.6 million years ago. Dr. Robert Boessenecker, study co-author and a vertebrate (脊椎動(dòng)物) paleontologist at the College of Charleston, commented: “We used the same worldwide dataset as earlier researchers and found that most of the dates had several problems—fossils with dates too young or imprecise, fossils that have been【C8】__, or old dates that have since been refined by improvements in geology; and we now know the【C9】__are much younger. The extinction of Otodus megalodon was previously thought to be related to that of the great white shark—but in reality, we now know the two are not【C10】_____related.”

[A] accepted [B] envy [C] excitement [D] hangs [E] ideal

[F] inherited [G] initially [H] major [I] obtained [J] original

[K] similarities [L] stands [M] time [N] ultimately [O] unsure

After three years of precise analysis, X-rays and infra-red (紅外線的) imaging, experts claim to have uncovered the only surviving portrait of William Shakespeare painted during his life. The canvas (油畫) is thought to have been painted in 1610—six years before the playwright’s death—when he was about 46 years old.

For three centuries the family who kept it was【C1】________of the identity of the figure in the portrait.

According to Alec Cobbe, an art restorer (做修復(fù)工作的人), at one【C2】________it had been thought to be of Sir

Walter Raleigh. In 2006, he visited the National Portrait Gallery and saw a painting of Shakespeare that【C3】_____in the Folger Shakespeare Library, Washington. It had been【C4】__as a life portrait of Shakespeare, but was denied 70 years ago. Mr．Cobbe saw the painting and realized the【C5】__with the painting he had【C6】_____.

Believing his painting to be the【C7】_____, he contacted Professor Stanley Wells, chairman of The Shakespeare Birthplace Trust, who was【C8】__skeptical. Prof. Wells said, “My first impression was skepticism—I am a scholar. But my【C9】__has grown with the amount of evidence about the painting. I am willing to go 90 percent of the way to declaring my confirmation that this is the only lifetime portrait of Shakespeare. It marks a【C10】_____development in the history of Shakespearian portraiture.”

The painting was displayed finally at The Shakespeare Birthplace Trust in Stratford-upon-Avon on April 23, Shakespeare’s birthday.

[A] activity [B] adopting [C] care [D] colleagues [E] compensated

[F] even [G] examined [H] familiar [I] injecting [J] rather

[K] reckon [L] research [M] similar [N] soared [O] synthetic

When children hit puberty (青春期), their ability to learn a second language drops. Why is this? Sheryl Smith and her【C1】_____at the State University of New York now【C2】_____that all of these behavioural changes could be due to a temporary increase in a chemical receptor that inhibits brain activity in an area responsible for learning.

In 2007, Smith’s team discovered that the number of these receptors【C3】_____in mice when they hit puberty, before falling back in adulthood. In their latest study, Smith’s team set about finding out if these receptors’ changes in mice might lead to impaired learning abilities,【C4】_____like those seen in pubescent humans.

The group【C5】________the hippocampus (海馬體) in mice’s brains. Sure enough, pubertal mice had seven times as many of the receptors as infant mice. In adulthood, the number of these receptors fell back to an intermediate level.

Smith reckons that the same mechanism might underlie the learning deficits teenagers experience. Cheryl Sisk at

Michigan State University at East Lansing agrees that “mice’s puberty is【C6】________to human puberty, although the timescale is different”.

In a further experiment, Smith found that she could remove the learning deficits by【C7】________pubertal mice with THP.

Smith suggests that in her most recent experiment, giving extra THP to pubertal mice increased their brain activity and that this activity may have【C8】________for their learning deficits.

Smith suggests that a【C9】_____form of THP could be developed for teenagers with learning difficulties, although she acknowledges that【C10】_____would need to be taken not to create any new problems.