— Why is it _________ Mr. Smith seldom mentions his childhood?
— Perhaps he suffered a lot in his childhood.
A：不填
B：what
C：how
D：that
下列叙述正确的是（）
已知关于x的方程x2-kx-6=0的一个根为x=3，则实数k的值为（ ）
Our teacher advises us exercise to keep healthy.
