在两个已知点上设站对待定点进行的测角交会方法称为()。
A.后方交会
B.前方交会
C.侧方交会
D.单三角形
参考答案:B
I didn't realize my mistake________my teacher had a facetoface talk with me.[ ]
A. until
B. after
C. since
D. when
造成污染的主控因素,内因是气象,外因是排放。