生活离不开化学，下列认识错误的是 [ ]

A．氦气可用于填充安全气球

B．用硬水洗涤衣物，既浪费肥皂也洗不净衣物

C．用洗涤剂除油污是因为洗涤剂能将油污溶解，形成溶液

D．在管道煤气中添加微量难闻气味的气体是为了及时发现煤气泄漏

The Parkers bought a new house, but_______will need a lot of work before they can move in.

A．they

B．it

C．one

D．which