2.16gX2O5中含有0.1mol氧原子，则X的相对原子质量为（ ）
A．14
B．28
C．21.6
D．31
答案：A
It was in the house ___he used to live that the exhibition was held.
A．where
B．that
C．as
D．which
“让少年儿童加入少先队”的具体目标是什么？
