问题

So difficult ____that no one could ___ a good solutionto it
A:must
B:can
C:should
D:would
B:can
C:should
D:would
正确答案是:
同类题型
She to beat the world record but failed at last.
diagnosed with cancer last month,but he carried on with his work ______ nothing had happened
Ann is in hospital- Oh, really? I _______ knowI _______ go and visit her
Would you like to go out to play football with me— ________, but I should finish my homework first.