Question

A. Although many theories​ exist, the reason for Amelia​ Earhart's disappearance remained a mystery. B. Although many theories​ exist, the reason for Amelia​ Earhart's disappearance remains a mystery. C. Although many theories​ exist, the reason for Amelia​ Earhart's disappearance is remaining a mystery. D. Although many theories are​ existing, the reason for Amelia​ Earhart's disappearance remains a mystery.

Answer 1

If you’re looking for the best worded answer, go for B.