Many people agree that _____ knowledge of English is a must in _______ international trade today. [ ]

A. a; /

B. the; an

C. the; the

D. /; the

当双务合同一方当事人的财产状况恶化致有不能履行其债务的危险时，如果该方当事人要求对方履行债务，对方有权抗辩。此种抗辩权称为（）。

A.同时履行抗辩权

B.先诉抗辩权

C.不安抗辩权

D.检索抗辩权