According to the rules of significant figures, the number of digits that are estimated in a measurement is:
a. one.
b. two.
c. three.
d. none.

According to the rules of significant figures in counting the number of significant figures when dealing with the measurement, especially when it is scientifically measured, you must consider 2 zeros at the right of the period. For example, in 98.00 there are 4 significant figures 

A= r2 × 3.14 7x7 ↓ ↓ 49 × 3.14 = 153.86 → 153.9