问题
选择题
Hearing the news about the crash of Air France Flight 447, he became very concerned _______ his daughter on board.
A．in
B．with
C．about
D．at
答案
答案：C
考查介词。be concerned about关心；挂念，句意：他非常关心他在国外的女儿。故用介词with，选C。
三种金属离子，现用NaOH，
，NaCl三种溶液使它们分别沉淀并分离出来，要求每次只加一种溶液，滤出一种沉淀，所加溶液顺序正确的是（ ）
