[A]: Centromere is the primary constriction on the metaphase chromosome.
[R]: It helps to separate sister chromatids

Options

A. (a) If both A and R are true and R is the correct explanation of A
B. (b) If both A and R are true but R is not the correct explanation of A
C. (c) If A is true and R is false
D. (d) If both A and R are false

Answer

B