Help please!!.Use estimation to check the answer to this story problem.

Priscilla had some stickers. She gave 21 stickers to her friends. She has 68 stickers left. How many stickers did Priscilla have to begin with?

A.70−20=□

The student's answer was reasonable.

B.60+20=□

The student's answer was not reasonable.

C.70+20=□

The student's answer was not reasonable.

D.70−30=□

The student's answer was not reasonable.

A student answered that Priscilla began with 47 stickers.

Which statement about the best estimation strategy for this problem is correct?