She looks very sad. I want to help her , but I just don’t know_________ to do.
The old man wears a set of false teeth when he eats.
—_____she your mother?—No, she _______. She’s my aunt.
下列表示重量单位的是______.
I have a tape player, _______ he doesn’t have one.
Please call me _______ 223-7118.