—What's the matter with Philips?

—Something must have happened to him. He left home three hours ago, but ________ at the party!

A．didn't arrive

B．isn't arriving

C．hadn't arrived

D．hasn't arrived

“物质的量”是国际单位制中的一个基本物理量，有关说法正确的是

A．2克H₂中含有1mol氢

B．1mol氧气的摩尔质量为32g

C．1mol任何物质都约含有6．02×10²³个分子

D．质量相等的O₂和O₃，它们的物质的量之比为3:2