将工作路径快速转换为选区的快捷键是（）。
A.Shift+Enter
B.Ctrl+Enter
C.Alt
D.Alt+Ctrl
参考答案：B
玉米根尖细胞所含的核酸中，含有碱基A、G、C、T的核苷酸种类数是[ ]
A．8
B．7
C．5
D．4
That passenger was very impolite to the conductor, ______, of course, made things even worse.
A．who
B．which
C．what
D．that
