如图所示，要粗测小明同学做“引体向上”时的功率。下面所列的物理量中，不需要测量的是
May I do my homework now，dad？
﹣Yes，you____（ ）
must
may
can
This is____friend，Sam．（ ）
I
my
me
﹣﹣May I come in？____，please．（ ）
Hold on
Sit down
Come in
Boys and girls，look____the blackboard，please．（ ）
at
out
in
I will never forget the people help me a lot in my life．（ ）
whose
when
which
who
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