15
choose the correct answer.
1 "have you ever lived in a big city before? "
"no, but i'm sure i will to it."
a be used bused © get used
2 "do you know that girl? "
"yes, we to go to the same school."
a are used b were used c used
3 "do you remember when we were children? " |
"yes, grandma always make us strawberry
muffins."
a would b got used to c was used to
4 "mr miller looks different now, doesn't he? "
"yes. he to wear glasses and have a
moustache."
a used b would c is used
5 "tom had trouble with the group project."
"yes. he to working with others."
a is used bisn't used cused
6 "amir has never done computer work before."
"don't worry, he will soon it! "
a be used b used to get used to
7 "do they find it difficult living in switzerland? "
"yes, they haven't the cold yet."
a been used to b got used to
c used
8 "why do you look so tired? "
"well, i to waking up so early."
a am not used bused
cam used
9 "do you have fond memories of
trips? "
"yes, my cousins go fishing by the
lake."
a would b were used c used
! !
So why did a change in climate 36,000 years ago drive the Siberian unicorn extinct, but not the woolly rhinoceros or the saiga?
To answer this question, our study took fossil bones from the Siberian unicorn, woolly rhino, and saiga, and looked at the nitrogen and carbon they contained — as differences in these elements reflect an animal's diet.
We found that before 36,000 years ago the saiga and the Siberian unicorn behaved very similarly, eating grass almost exclusively. After this point, the carbon and nitrogen in saiga bones showed a major dietary shift towards other plant types.
But shifting from a grass diet proved too difficult for the Siberian unicorn, with its special folded wear-resistant teeth and a low-slung head right at grass height.
Relatives such as the woolly rhino had always eaten a more balanced array of plants, and were much less impacted by a change in habitat.
Importantly, the change in climate that drove the Siberian unicorn extinct was actually much less pronounced than those which occurred during the Ice Age that followed. Or the changes that we will face in the near future.
The story of the Siberian unicorn is a timely reminder that even subtle changes in plant distributions can have devastating knock-on effects for large animal species.
Legends of the unicorn, or a beast with a single horn, have been around for millennia.
Some have argued that the horn of the rhino may have been the basis of myths about unicorns, although other animals - such as the tusked narwhal - are more likely contenders.
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