Frequency of Down syndrome increases when maternal age is above 35 years.
In aged mother nondisjunction of 21st chromosome during oogenesis occurs more frequently.

Options

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

Answer

A