问题补充:
I admit that all these problems are difficult, I don’t agree that they can’t be solved.
A. Unless
B. While
C. Until
D. Since
答案:
A. Unless
(答案→)B. While
C. Until
D. Since
解析: 词义辨析。Unless除非……否则;While尽管;Until直到;Since
自从,因为,由于。句意:尽管我承认这些问题都很难,但是我不认为它们不能被解决。所以选B。