Before replacing a piston you should check the rings to see that all clearances and gaps are within the permissible （）.

[试题]B．eforeyoumailthisletter，youshouldcheckagainwhetheryouhave_______itornot.A.sunkB.sighedC.soughtD.sealed

[问答题]You should look around before you cross the street.

[单选题]You should [convert]RMB into foreign currency before you go abroad.A.alterB

[单选题]You should have [blended]the butter with the sugar thoroughly before you he

[单选题]You should have [blended]the butter with the sugar thoroughly before you he

[单选题]What should be prepared before disassembly of cylinder for main engine or auxiliary engine?

[单选题]You should work for __________ if you become an editor of the magazine.A． just nine hours a dayB. no less than nine hours a day C. about ten hours a dayD. less than 25 hours a week

[单选题]_____you may have, you should gather your courage to face the challenge.A． However a serious problemB． What a serious problemC． However serious a problemD． What serious a problem

[单选题]H．ow many tablets should one take before he goes to sleep?A．oneB．twoC．one and halfD．three

[单选题]---What should I do first before boarding? ----().A．You may ask the policeman there to help.B．Please go to the airline counter to check-in for your flight.C．You should wait and see.D．You have to go there to check in for your flight.