如图所示,当开关S闭合时,电路的闭环电压放大倍数等于()。
A.-3
B.-5
C.-4
D.-7
参考答案:A
用噬菌体侵染含大量的3H的细菌,待细菌解体后,3H [ ]
A.随细菌解体而消失
B.仅发现于噬菌体的外壳中
C.仅发现于噬菌体的DNA中
D.发现于噬菌体的外壳及DNA中
补全对话。
A: season do you like best, Jenny?
B: Well, in Beijing I like fall . The sky is . The leaves is red.
A: Which season do you best?
C: I like best. I can play the snow.
A: Winter is beautiful, but it's too for me. I like summer best. I like swim in the sea.
B: Summer is best, but fall is my season.
C: Why?
B: Halloween and Thanksgiving!