色谱分析中，相邻两峰能否完全分开的标志是（）
A.R=1.0
B.R=1.5
C.R=2.0
D.R=2σ
参考答案：B
—You didn’t wait for Mr. Black last night, did you?
—No, but we ____. He didn’t return home at all.
A．couldn’t have
B．needn’t have
C．didn’t need to
D．should wait have
隔代家庭的咨询要点有哪些？
