Since English biologist Charles Darwin published On the Origin of Species in 1859, scientists have vastly improved their knowledge of natural history.However, a lot of information is still the subject of speculation, and scientists can still only make educated guesses at certain things. One subject that they guess at is why some 400 million years ago, animals in the sea developed limbs that allowed them to move onto and live on land. Recently, an idea that occurred to the US paleontologist ( 古生物学家 ) Alfred Romer a century ago became a hot topic once again. Romer thought that tide pools might have led to fish gaining limbs.Sea animals would have been forced into these pools by strong tides.Then, they would have been made either to adapt to their new environment close to land or die.The fittest among them grew to accomplish the transition from sea to land. Romer called these earliest four­footed animals “tetrapods” . Science has always thought that this was a credible theory, but only recently has there been strong enough evidence to support it. Hannah Byrne is an oceanographer ( 海洋学家 ) at Uppsala University in Sweden.She announced at the 2018 Ocean Sciences Meeting in Oregon, US, that by using computer software, her team had managed to link Romer's theory to places where fossil deposits of the earliest tetrapods were found. According to the magazine Science, in 2014, Steven Balbus, a scientist at the University of Oxford in the UK, calculated that 400 million years ago, when the move from land to sea was achieved, tides were stronger than they are today.This is because the planet was 10 percent closer to the moon than it is now. The creatures stranded in the pools would have been under the pressure of “survival of the fittest” , explained Mattias Green, an ocean scientist at the UK's Bangor University.As he told Science, “ After a few days in these pools, you become food or you run out of food ...The fish that had large limbs had an advantage because they could flip ( 快速翻转 ) themselves back in the water. ” 8 . Who first proposed the theory that fish might have gained limbs because of tidal pools? A . Alfred Romer. B . Charles Darwin. C . Hannah Byrne. D . Steven Balbus. 9 . Why were tides stronger 400 million years ago than they are today according to Steven Balbus? A . There were larger oceans. B . Earth was closer to the moon. C . The moon gave off more energy. D . Earth was under greater pressure. 10 . The underlined word “stranded” in the last paragraph probably means “________” . A . found B . settled C . abandoned D . trapped 11 . What is the focus of the article? A . The arguments over a scientific theory. B . The proposal of a new scientific theory. C . Some new evidence to support a previous theory. D . A new discovery that questions a previous theory.