Which of the following organ keeps on decreasing in size with age?

The correct answer is Option (1) –Thymus

The thymus is the organ that continuously decreases in size with age (a process called involution).

Thymus: The thymus is a lobed organ located near the heart and beneath the breastbone. The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. Both bone-marrow and thymus provide micro-environments for the development and maturation of T-lymphocytes.

Other options:

• Adam’s apple: Grows during puberty (due to larynx enlargement) and stays stable in size.
• Stomach: Size doesn’t decrease with age (though acid production might).