槽形托辊一般由（）个短托辊组合而成，槽角一般为30°。
A.3
B.2
C.1
D.5
参考答案：A
More trees ______ around our city every spring. [ ]
A. plant
B. planted
C. are planted
D. were planted
AAA级定点医疗机构可以免检。
