单选题Crankshafts of medium speed engines are （） from a single piece of steel.Aunusually solid weldedBnever be solid forgedCalmost invariably solid forgedDalmost invariably be welded
单选题
Crankshafts of medium speed engines are （） from a single piece of steel.
A
unusually solid welded
B
never be solid forged
C
almost invariably solid forged
D
almost invariably be welded
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