In the Following Diagrams,A Represents a Radioactive Isotope That Decays

In the following diagrams,A represents a radioactive isotope that decays into a new isotope,X.Each circle represents 1 mmol of atoms. t = 0: t = 25.0 s: Over the first 25.0 s,what is the disintegration rate of A?

A) 0.120 disintegrations per second
B) 1.81 × 10²¹ disintegrations per second
C) 3.00 disintegrations per second
D) 7.23 × 10¹⁹ disintegrations per second
E) 1.38 × 10^-20 disintegrations per second