Much to my surprise Alan suddenly _________song.
A. burst from
B. burst into
C. burst at
D. burst upon
查看答案
David got a job in an important New York law office two years after he _________Harvard.
A. graduated from
B. graduated at
C. graduated in
D. graduated to
Mrs. Smith plans to retire from office as soon as all her children are _________.
A. self-employed
B. self-made
C. self-supporting
D. self-respecting
No _________doctor would refuse to treat a sick person.
A. self-employed
B. self-made
C. self-supporting
D. self-respecting
555定时器构成的单稳态触发器的暂稳态的持续时间为
A. 1.5RC
B. RC
C. 1.8RC
D. 1.1RC
微信支付 
支付宝支付