Would you please tell me________to deal with all the problems, Mr Feng?
A:how
B:why
C:what
D:which
“甘瓜抱苦蒂,美枣生荆棘”,启示我们塑造美好人生需要( )
玻璃中加入二氧化钒可以有选择地吸收和反射色光,二氧化钒(VO2)中钒元素的化合价为( )