Choose the most appropriate article from the given options to fill in the blank :

Shyam's hostelmate has become _________ IAS officer.

An

The most appropriate article to fill in the blank is: An

The choice of the article depends on the pronunciation of the following word. In this case, "IAS" is pronounced with a vowel sound at the beginning (pronounced as "eye-ay-es"). When a word begins with a vowel sound, we use the indefinite article "an" before it. Therefore, the correct choice is "an IAS officer."