—Has your father finished his report?

—Sorry, I don't know. He _______ it this morning. [ ]

A. was writing

B. wrote

C. has written

D. had written

在经纬仪观测水平角和竖直角的过程中，仪器对中误差产生最大影响时，是角度按近（），与测边呈垂直方向。

A．90°

B．180°

C．0°

D．270°