From the author’s point of view， language should be looked upon as a road map and a valuable possession：often study the road map（check ） and tune up the car engine（adjust ）.

From the author’s point of view， language should be looked upon as a road map and a valuable possession：often study the road map（check ） and tune up the car engine（adjust ）.
A.guide book； gear
B.gear； guide book
C.vocabulary； grammar
D.grammar； vocabulary
正确答案：grammar； vocabulary