Ⅲ. Key structures. 关键句型。
A) Underline the present progressive, passive voice, present perfect and modal verbs in the passage. 画出课文中表示现在进行时、被动语态、现在完成时的动词和情态动词。
B) Give the correct forms of the verbs in parentheses. Do not refer to the passage until you finish your exercise. 用括号中所给动词的正确形式填空，完成练习后再对照课文，核对你的答案。
Many have heard of shark fin soup. This famous and expensive dish is specially popular in southern China. But do you realize that you (kill) a whole shark each time you enjoy a bowl of shark fin soup?
When people catch sharks, they cut off their fins and throw the sharks back into the ocean. This is not only cruel, but also harmful to the environment. Without a fin, a shark no longer (swim) and slowly dies. Sharks are at the top of the food chain in the ocean's ecosystem. If their numbers drop too low, it will bring danger to all ocean life. Many believe that sharks never (be) endangered because they are the strongest in their food chain. But in fact, around 70 million sharks (catch) and (trade) in this industry every year. The numbers of some kinds of sharks (fall) by over 90 percent in the last 20 to 30 years.
Environmental protection groups around the world, such as WildAid and the WWF, (teach) the public about "finning". They even (ask) governments to develop laws to stop the sale of shark fins. So far, no scientific studies (show) that shark fins are good for health, so why eat them? Help save the sharks!

are killing, can, swim, can, be, are caught, traded, have fallen, are teaching, have, asked, have shown