哪个不是预防“假期综合症”的方法（）。
A、假期前的心理调适
B、休息要适当
C、多和朋友接触
D、多想开心事
参考答案：C
This is the only one of the oldest customs that ________ down in this area so far.
A．was kept
B．were kept
C．has been kept
D．have been kept
矿物
