投资者委托买卖证券后,其中一部分已成交,下列说法正确的是()。
A. 所有委托均不得撤单
B. 已成交部分不得撤单,但未成交部分可以撤单
C. 买入证券不得撤单,卖出证券可以撤单
D. 卖出证券不得撤单,买入证券可以撤单
【B2】
A. in
B. on
C. at
D. over
听力原文:M: You're going to wear out that typewriter.
W: Oh, hi. What are you doing here at this time of night?
M: I should ask you that question. Do you have any idea what time it is?
W: About ten or ten-thirty?
M: It's nearly midnight.
W: Really? t didn't have any idea it was so late.
M: Don't you have an early class tomorrow morning?
W: Yes, at seven o'clock. My part-time class, for the students who go to work right after their lesson.
M: Then you ought to go to bed.
W: Ok.
When is the conversation taking place?
At ten.
B. At ten-thirty.
C. Nearly at midnight.
【B20】
A. sign
B. symbol
C. mark
D. feature