题目内容：

Read the passage and choose the best answer（根据短文内容，选择最恰当的答案）：

Dinosaurs were the dominant land animals for 160 million years, making them one of the most successful groups of animals ever. However, all the dinosaurs that were living 65 million years ago went extinct. About 70% of all animal life on the earth died out. Scientists call it a mass extinction（大灭绝）.

Having existed for 165 million years, why did dinosaurs die out? There are many different theories about why this happened. We will probably never know exactly what happened, which means that scientists will continue to disagree and come up with different dinosaur extinction theories. Here are two of them:

Ice Age Theory

Now and again, the earth cools into periods we call ice ages. As dinosaurs were thought to be cold blooded, it was hard for them to cope with such cold conditions.

Disease

It is possible that a disease spread through the dinosaur population causing their extinction.

Scientists have come up with some strange ideas but none of the theories really explains everything, so we will probably never be sure what happened.

1.The underlined word “dominant” in the passage probably means _________.

A.biggest B.powerful C.strange D.special

2.Why did the dinosaurs become extinct? ___________.

A.Dinosaurs could not suffer from cold weather B.A disease spread through the dinosaur population

C.Other species became stronger than dinosaurs D.We have not known about the truth yet

3.Dinosaurs existed on the earth for _______ million years.

A.160 B.165 C.65 D.115