It may be necessary to stop ______in the learning process and go back to the difficult points in the lessons.

A．)at a distance                B)at intervals

C．)at case                    D)at length

[单选题]It is necessary that anyone ______exercises every day if he wishes to keep healthy.A． doB． would doC． didD． will do

[单选题]If it becomes necessary for a stand-on vessel to take action to avoid collision，she shall NOT，if possible，().A．Decrease speedB．Increase speedC．Turn to port for a vessel on her own port sideD．Turn to starboard for a vessel on her own port side

[单选题]When it is necessary to remove a victim from a life threatening situation，the person giving first aid must ().A．Pull the victim by the feetB．Avoid subjecting the victim to any unnecessary disturbanceC．Carry the victim to a location where injuries can

[问答题]It is not necessary to do this work.

[问答题]It is necessary to take medicine on time

[单选题]It is possible，and sometimes necessary，to strengthen the deck of a vessel for carriage of deck cargo by（）.A . placing bunker on the deckB . building a stage on which to place the cargoC . welding steel feet to the deck，on which the cargo is placedD .

[单选题]It is necessary to remove （） from the cooling spaces.A . scarB . scaleC . spurD . bilge

[单选题]It is very necessary that each cylinder （） before the charged air is compressed.A . is scavengedB . is atomized with fuel oilC . be scavengedD . be atomized with fuel oil

[单选题]Itisquitenecessaryforaqualifiedteachertohavegoodmannersand_________knowledge.A．)extensiveB)expansiveC．)intensiveD)expensive

[单选题]It is quite necessary for a teacher to have good manners and__________ knowledge．A．extensiveB．expensiveC．intensiveD．expressive