Step 1: Quote the article.
Article 80(1)(a) authorizes the President to {nominate 12} members to Rajya Sabha for special knowledge or practical experience in literature, science, art or social service.
Step 2: Rationale of nomination.
The nomination route brings non-electoral expertise into parliamentary deliberation (e.g., celebrated artists, scholars).
Step 3: Eliminate others.
14/16/18 are not recognized nomination counts in Article 80.
Step 4: Conclude.
\[
\boxed{\text{12 (Option A).}}
\]