地理实践活动课上,老师要求学生们在展板上制作校园平面图,比较合适的比例尺是( )
A:1:1000000
B:1:100
C:1:10 000
D:1:100 000
The teachers' office is on the second floor.
—I often take a dancing class.
传染病的传染源是指( )