Assertion $(A)$: In aqueous solution,$\alpha$-amino acids exist as an internal salt called a zwitter ion.
Reason $(R)$: Proline is a natural amino acid having a secondary amino group. 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