—I called you just now, but you weren't in.

—Oh, sorry. I _______ outside.      [ ]

A. was taking a walk  

B. talked with my friend

C. went shopping

用一种试剂鉴别盐酸、氯化钠和氢氧化钙三种溶液，应选用的是 [ ]

A．稀硫酸

B．碳酸钠溶液

C．氯化钡溶液

D．氢氧化钾溶液