单项选择题
C2H4的制冷剂代号为( )。
A.R150
B.R15
C.R1150
D.R22
C2H4的制冷剂代号为( )。
A.R150
B.R15
C.R1150
D.R22
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单项选择题
From Billy, we know that, to be successful, we must learn to be _______.
From Billy, we know that, to be successful, we must learn to be _______.
A.independent
B.diligent
C.elegant
D.persistent