--The English exam is not difficult, is it?

--________. Even Tom ________ to the top students failed in it.

A．Yes; belongs

B．No; belonged

C．Yes; belonging

D．No; belongs

下列判断正确的是（）。

A．AsH₃、MgO都是共价化合物

B．AsH₃、HCl都是共价化合物

C．CaF₂、AsH₃都是离子型化合物

D．CaF₂、SO₂都是共价化合物