Our family were thinking about __________ Hainan Island at this time yesterday.

                                                                                                                                                        [ ]

A. to visit

B. Visited

C. visiting

D. visit

中线测量中，转点ZD的作用是（）。

A.传递高程

B.传递方向

C.传递桩号

D.A，B，C都不是