问题补充：
Thousands of foreigners were to the Shanghai World Expo the day it opened.
A. attended
B. attained
C. attracted
D. attached
答案：
A. attended
B. attained
(答案→)C. attracted
D. attached
解析：动词辨析。Attend参加某种学术会议； attain达到，实现；attract吸引，引起；attach附加，贴上。句意：上海世博会开幕那天吸引了无数的外国人。故选C。
