Question

The experiment shows that proper amounts of exercise, if ______ regularly, can improve our health.

A．being carried out

B．carrying out

C．carried out

D．to carry out

Answer 1

C

试题分析：考查状语从句的省略句：当主从句的主语一致的情况，可以省略从句的主语和be动词，If carried out="if" proper amounts of exercise are carried out。句意：实验表明，适量的锻炼，如果被定期进行，能提高人们的健康。选C。
点评：如果主句的主语和从句的主语一致，且状语从句的谓语动词中有 be 动词，从句的主语连同be 可一起省略，该类状语从句多为时间、地点、条件、方式或让步等，连词为when, while, though, if, unless, although, as if 等，后面通常接分词、不定式、形容词、名词等。