Solution: period: s = 3.14× (2r) 2-3.14r2 = 9.42r2;

Comma: s =

1

2

×3. 14×(2r)2 = 6.28 R2；

Question mark: s =

three

four

×[3. 14×(2r)2？ 3. 14r 2]+3. 14r 2 = 10.205 R2；

Because 10.205R2 > 9.42R2 > 6.28R2,

Therefore, the pigment of the question mark is much used.