饭店代表在向介绍饭店历史文化时，应避免涉及到（）。
A、其他饭店在历史文化方面的缺陷
B、曾经接待的重要客人
C、发展背景
D、开业日期
参考答案：A
—Look at the boy running on the ground. Is it David?
—It _____be him. I saw him go to the teacher's office just now. [ ]
A. might
B. could
C. can't
D. mustn't
从科研领域考虑，科研论文一般分为（）；（）；（）；（）等基本类型。
