问题
选择题
Jim couldn’t understand how the machine worked until his friends____ how to use it.
A.promised
B.explained
C.thought
D.heard
答案
答案:B
考查词义辨析。promised 答应,允诺,explained解释,thought认为,heard听到,句意:吉姆不明白这台机器如何工作直到它的朋友们解释了如何使用。所以选B。