下列属于有效证件的是（）。
A、护照
B、军官证
C、游泳证
D、学生证
参考答案：A, B
The maths teacher asked Alice _____ yesterday. [ ]
A. why she misses school
B. why does she miss school
C. why she missed school
D. why did she miss school
航空运单第一份蓝色运单交给托运人，由承运人留存作为内部记账凭证。( )
