It is (undoubtedly) true that the Watergate scandal was the worst
in U.S political history
A. Considerably
B. arguably
C. indecisively
D. without question
=> undoubtedly = without question : ko còn nghi ngờ gì nữa
=> thêm cấu trúc :
It is undoubtedly true that = It is beyond the shadow of a doubt that = It is without question that