单项选择题
A.reaches to B.gets C.calls on D.calls at
（）does it take to change the main engine from ahead to ...
单项选择题（）does it take to change the main engine from ahead to astern?
A.How many times B.How much water C.How long D.How length
（）, we continued lifting out the pistons.A.Late as it w...
单项选择题（）, we continued lifting out the pistons.
A.Late as it was B.As it was late C.Since it was late D.Because of its late
The exhaust valve is opened at about the same time （） t...
单项选择题The exhaust valve is opened at about the same time （） the air inlet ports are opened.
A.before B.after C.when D.until
