问题

Within the last year, scientists have come closer than ever .
A:to deciding which of the questions is right
B:to decide which of the questions is right
C:deciding whether the question is right or not
D:and decided which of the questions is right
B:to decide which of the questions is right
C:deciding whether the question is right or not
D:and decided which of the questions is right
正确答案是: