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【单选题】
51单片机的4个并行I/O端口作为通用I/O端口使用,在输出数据时,必须外接上拉电阻的是( )。A.
P0
B.
P1
C.
P2
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反馈参考答案：
举一反三
【单选题】------I have just had my watch repaired. ------How much did they ____ for that?
A.
cost
B.
charge
C.
spend
D.
pay
【单选题】--- Oh, it’s you! I ___________ you. ---- I have just had my hair cut, and I am wearing new glasses.
A.
didn’t recognize
B.
don’t recognize
C.
haven’t recognized
D.
hadn’t recognized
【单选题】某化合物的相对分子质量 M r =72, 红外光谱指出 , 该化合物含羰基 , 则该化合物可能的 分子式为( )
A.
C 4 H 8 O
B.
C 3 H 4 O 2
C.
C 3 H 6 NO
D.
C 4 H 8 O 或者 C 3 H 4 O 2
【单选题】某化合物的相对分子质量 M r =72,红外光谱指出,该化合物含羰基,则该化合物可能的分子式为 ( )
A.
(1) C 4 H 8 O
B.
(2) C 3 H 4 O 2
C.
(3) C 3 H 6 NO
D.
(4) (1) 或（2）
【单选题】—I have just had my watch repaired. —How much did they ________ for that? [ ]
A.
cost
B.
charge
C.
spend
D.
consider
【单选题】— I have just had my watch repaired. —How much did they ______ you?
A.
pay
B.
charge
C.
cost
D.
spend
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