问题补充:
Jim was walking along the river he heard someone Help! Help!
A. when; shout
B. while; shouting
C. as; to shout
D. when; shouting
答案:
A. when; shout
B. while; shouting
C. as; to shout
(答案→)D. when; shouting
解析:句意:Jim正沿着河边散步,这时他听到有人喊:“救命”。第一空when 的意思是,正在这时;while 和as 都是当…时候;hear sb. doing 听到某人正在做某事。根据句意可知选D。