暗物质一定参与()。
A、电磁相互作用
B、强相互作用
C、弱相互作用
D、引力相互作用
参考答案:D
—I’m trying to find yesterday’s paper. Have you seen it?
—I’m afraid I ______ it away. I thought you had finished reading it.
A.had thrown
B.throw
C.would throw
D.threw
纸类包装材料包括()
A、纸张
B、纸板
C、木罗纸板
D、加工纸类