单项选择题
A. though doing
B. though done
C. if done
D. if doing
单项选择题 Having been praised by the teacher, the little girl ran back home, ().
单项选择题 By the end of last week. 611 people from 49 countries () to attend the meeting, with nearly half coming from the United States, Germany and Britain.
单项选择题 The doctor tried to do an experiment to find out the () of the medicine on the mice.