“I'm polly”中的“'”符号时省略了哪个英文字母？ （)

My roommate Rob made a （)with me that he' d give me his girlfriend Polly in ex

change for my jacket. And I agreed.

Polly had the right background to be the girlfriend of a ()lawyer like myself. She was pretty, well-off, and radiant. Sill, | want to dispense her enough () to make her “well-spoken”.

A.“K”和“O”

B.“I”和“O”

C.“N”和“O”

D.“I”和“M”

“I don't know”中的“'”符号时省略了哪个英文字母？ ()

当肌纤维收缩时，细肌丝向A带中的M线方向滑动，导致H带和I带变（)。

有一保守力F=(-Ax+Bx²)i，沿x轴作用于质点上，式中A、B为常量，x以m计，F以N计．

⑴取x=0时 Ep=0，计算与此力相对应的势能；

⑵求质点x=2m运动到x=3m时势能的增量。

A.t

B.kg

C.ns

D.μm

A.m²

B.m³

C.n²

D.n³

A.m³

B.m²

C.n²

D.n³