单选题The two-stroke cycle begins with the piston coming up from the BDC, with the scavenging ports in the sides of the cylinders being （）.AopenBuncoverCcoveredDclosed
单选题
The two-stroke cycle begins with the piston coming up from the BDC, with the scavenging ports in the sides of the cylinders being （）.
A
open
B
uncover
C
covered
D
closed
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