Câu hỏi:

Supply the correct tense or form of the verbs in brackets to complete the passage. Write your answers in the numbered table below. (0) has been done as an example.

18,000 years ago, much of Europe (0) ________(lie)  (1)________(bury) beneath vast sheets of ice, hundreds of metres thick. Ever since this astonishing fact (2)_______(discover)  in the last century, scientists (3) ________(speculate) on the nature of the Ice Age climate, and the circumstances that brought it to an end. More recently, people (4) ________(wonder)  if climatic changes could (5)________(take) place in our own time. During the early 1970s there (6)_______(be) disastrous droughts in Africa, and frequent failures of Indian monsoon. In 1976, Europe sweltered in the hottest summer for over a century, and (7)_______(experience) one of the worst droughts since records began. Could such events as these be symptoms of a worldwide climatic shift? Even small changes in climate that (8)________(occur)  from time to time can have a highly damaging effect on agriculture. With food reserves now (9)________ (stand) at only a few per cent of annual production, the world is extremely vulnerable (10) ________(adverse)  shifts in climate. It is therefore vitally important for us to understand how climate changes take place.

18,000 years ago, much of Europe (0) ________(lie)  (1)________(bury) beneath vast sheets of ice,