Ⅱ阅读（共两节，满分50分）
第一节阅读理解（共20小题；每小题2分，满分40分）
阅读下列短文，从每题所给的A、B、C和D项中，选出最佳选项，并在答题卡上将该项涂黑。
A
Imagine living in a city made of glass. No, this isn’t a fairy tale. If you could grab your diving gear and swim down 650 feet into the Pacific Ocean off the coast of Washington State, you would witness the secret world of glass reefs.
The reef you’d be looking at is made up of glass sponges(海绵). But how can animals be made of glass? Well, glass is formed from a substance called silica. The sponges use the silica found in ocean waters to build glass structures that will give them shape and support. Be careful! Some of the fragile creatures are up to 200 years old.
When sponges die, new ones grow on top of the pile of old ones. Over centuries, a massive and complex reef takes shape. Some sponges look like wrinkled trumpets, while others look like overgrown cauliflower or mushrooms.
