单项选择题
A.Late as it was
B.As it was late
C.Since it was late
D.Because of its late
单项选择题 The exhaust valve is opened at about the same time （） the air inlet ports are opened.
单项选择题 When entering a foam injected space （） breathing apparatus.
单项选择题 The exhaust ports are located around the lower part of the cylinder liner, （）the products of combustion are driven by scavenging air.