债权人甲以买卖合同书证明他与债务人乙之间存在买卖法律关系，此买卖合同书属于（）
A.间接证据
B.物证
C.反证
D.书证
参考答案：D
— I am worried I can't get into a good high school because I'm weak ______ English.
— Don't worry. ______ and asking a teacher for help can help a lot. [ ]
A. in; Work hard
B. in; Working hard
C. at; Working hard
D. at; To work hard
曲线上设置超高的作用之一是为了抵消和减少汽车的离心力的影响。（）
