挖掘机上坡时，驱动轮应在后面，臂杆应在上面;挖掘机下坡时，驱动轮应在前面，臂杆应在后面。上下坡度不得超过（）度。
对外贸易统制集中表现在______
Mr.Smithisingoodhealthnowforitisquitealongtimesincehe__________.
Theboyboughtanewdictionary__________heturnedforhelp.
Theteacheraskedthechildren_____they_____thethingsintheladthatmorning.
Heaskedme_________.
