题目内容：

    Scientists think they have the answer to a puzzle that confused even Charles Darwin： How flowers evolved and spread to become the most important plants on earth．

Flowering plants, or angiosperms (被子植物), make up about 90% of all living plant species,but how they did this has been a mystery. New research suggests it is due to genome (基因组) size．

Hundreds of millions of years ago,the earth was dominated by ferns (蕨类)and conifers(针叶树) - they were the main plants on the earth． Then, about 150 million years ago， the first flowering plants appeared on earth. They quickly spread to all parts of the world．

Why angiosperms were successful and diverse on earth has been debated for centuries.Charles Darwin himself called it a "mystery", fearing this apparent sudden change might challenge his theory of evolution．

Kevin Simonin from San Francisco State University in California US and other researchers analyzed data held by the Royal Botanic Gardens, Kew， on the genome size of hundreds of plants, including flowering plants, gymnosperms (a group of plants including conifers) and ferns. They then compared genome size with anatomical (结构上的) features. This provides "strong evidence" that the success and rapid spread of flowering plants around the world is due to "genome downsizing"．

By reducing the size of the genome, which is contained within the nucleus (核) of the cell, plants can build smaller cells. The researchers say genome-downsizing happened only in the angiosperms, and this was "a necessary condition for rapid growth rates among land plants"．

1.What do we know about angiosperms？ ______

A.They are superior in number among all living plant species．

B.They controlled the earth for hundreds of millions of years．

C.They challenge Charles Darwin's theory．

D.They are extinct plants in the world．

2.It can be implied that ______ ．

A.Simonin works in the Royal Botanic Gardens Kew

B.Simonin is probably an American biologist

C.Darwin was confident of his theory of evolution

D.Darwin succeeded in figuring out the flower evolution

3.What contributed to the success and diversity of angiosperms？ ______

A.The weaker ferns and conifer．

B.The larger nucleus．

C.The stronger cell．

D.The smaller genome．

4.What can be a suitable title of this passage？ ______

A.Why were gymnosperms successful on earth？

B.What puzzle confused even Charles Darwin？

C.Why angiosperms dominated the earth？

D.When angiosperms outnumbered conifers and Ferns？