Explanation:

Let’s break it down:

- Option 1: Article 339

- Article 339 gives the President the power to appoint a Commission to report on the administration of Scheduled Areas and the welfare of Scheduled Tribes. It’s specifically about Tribes, not both SCs and STs, and focuses more on administration and welfare.

- Option 2: Article 250

- Article 250 deals with Parliament’s power to legislate on subjects in the State List if there’s a national emergency. It has nothing to do with SCs or STs.

- Option 3: Article 338

- Here’s the answer. Article 338 creates the National Commission for Scheduled Castes and Scheduled Tribes (now split into two commissions). It specifically says the President will appoint the Commission, which reports annually on the safeguards and rights for these groups.

- Option 4: Article 259

- This is about borrowing armed forces of the Union for state use and has nothing to do with SCs, STs, or their rights.

So, to sum up, Option 3: Article 338 is absolutely the right choice for your question.