单项选择题
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
When entering a foam injected space （） breathing appara...
单项选择题When entering a foam injected space （） breathing apparatus.
A.put out B.put on C.take off D.take in
