Assertion $(A)$: Ammonia and its derivatives of the form $H_2N-Z$ undergo condensation reaction with carbonyl compounds (aldehydes and ketones).
Reason $(R)$: This reaction is an example of an irreversible reaction.
The correct option among the following is:

• A
  $A$ is true,$(R)$ is true and $(R)$ is the correct explanation for $(A)$
• B
  $A$ is true,$(R)$ is true but $(R)$ is not the correct explanation for $(A)$
• C
  $A$ is true but $(R)$ is false
• D
  $A$ is false but $(R)$ is true