Assertion (A): Human development measures how much socioeconomic development has happened in a country.

Reason (R): Comparison of national income of two countries explains human development index.

A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is not the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.