两种材料之间的摩擦系数μ与他们之间的摩擦角ψ的关系为μ=（）。
A.sinψ；
B.cosψ；
C.tgψ；
D.tcgψ。
参考答案：C
用所给单词的正确形式填空。
1. Today is February _________ (fifteen).
2. I _________ (eat) the ice cream yesterday.
3. I wanted _________ (fly) a kite, but it _________ (be) too hard.
4. I hurt _________ (I) arm and Jenny helped _________ (I).
5. You were _________ (sleep) on the train.
温热药可使寒证患者血中儿茶酚胺含量减低。（）
