第二节 语法填空（共10小题；每小题1.5分，满分15分）
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为11-20的相应位置上。
To most of us, sharks are _31__ most dangerous fish in the sea, for they attack humans. However, according to Doctor Clark, ___32___ has studied the behavior of sharks for twelve years, humans are not normally on a shark’s menu. What ___33___ sharks feed on? Mainly fish and other small sea animals.
