判断文中所使用的词汇和短语的正确意思；

滚动浏览(scrolling)就是利用电脑的滚动条在屏幕上迅速移动文章。当文章太长、无法同时看到全文的时候，考生必须要通过滚动文章来浏览全文。考生无论是略读文章纵览全文，还是浏览段落寻找细节，滚动浏览都是非常重要的一项辅助技能。

D. Many people are upset that stem cells are taken from aborted fetuses and that human embryos are created for the sole purpose of extracting stem cells.

[1]  It should be obvious that cetaceans whales, porpoises, and dolphins-are mammals. They breathe through lungs, not through gills, and give birth to live young.  Their streamlined bodies, the absence of hind legs, and the presence of a fluke and blowhole cannot disguise their affinities with land dwelling mammals.  However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but already fully marine cetaceans are known from the fossil record.  How was the gap between a walking mammal and a swimming whale bridged?  Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.

C.