Engines are to machines _________ hearts are to animals. A．asB．thatC．whatD．which
Engines are to machines _________ hearts are to animals.
C解析:
此题主要测试以下句型结构：A is to B what C is to D。意思：A对于B的重要性，就如同C对于D的重要性一样。此句型中what从句在主句中起表语作用，同时what在从句中也起表语作用（这一点老师应该掌握，然而学生只需记住该句型结构即可）。例如：Railway is to transportation what blood is to a man's body。铁路对于交通的重要性，就如同血液对于身体的重要性一样。
