已知⊙O的半径是3cm，点P和圆心的距离是6cm，过点P作⊙O的两条切线，则两切线的夹角是（ ）度。
60
So clearly _____ that I was able to understand much of what he said. [ ]
A. did he say
B. he told
C. did he speak
D. he talked
盖布瑞尔合成法可用来合成下列哪种化合物？（）
A.纯伯胺
B.纯仲胺
C.伯醇
D.混合醚
