用于识别运行方向的应答器组应至少包括（）个应答器。
A.1
B.2
C.3
D.4
参考答案：B
We were _____ happy to know the manned spaceship Shenzhou VI landed on the earth successfully. [ ]
A. more than
B. other than
C. rather than
D. less than
食物中毒发病特点的核心是（）
A.呈暴发性
B.有相似的临床表现
C.发病与食物有关
D.对健康人无传染性
E.发病曲线无余波
