Question

There is no point advocating banning smoking in public ________ the law is introduced.

A．when	B．unless
C．since	D．because

Answer 1

B

B 考察连词。句义：除非成为法律条文，否则在公共场所倡议禁止吸烟是没有意义的。When当..时；unless除非；since自从；because因为；故B正确。