问题

To keep the air fresh during the night, I often sleep with the windows on ________ it’s really cold.

A:unless
B:if
C:because
D:when;

正确答案是：

同类题型

There are ____ people in the train.

We should think of the problems that may ____ in the future.

day Mr. Li finally bought his ownhouse, _______ is a hospital.

The cancer risks____withsmoking have been well documented.[ ]

vernment officials met the workers and engineersworking on the stadium, most _________ being migrant workers.