【题目】（题文）________ abstract, Galileo's theory was quite difficult to understand of his time.
A. Sounded B. To sound
C. Sounding D. Having been sounded
在线课程【答案】C
【解析】
考查非谓语动词。句意：因为听起来很抽象，伽利略的理论在他的那个时代很难理解。分析句子可知，sound用非谓语动词形式，与其逻辑主语Galileo's theory为主谓关系，sound表示“听起来”是系动词，无被动式，故用现在分词sounding，故选C。