Select the most appropriate option to fill in the blank and make a grammatically correct sentence.

It was ______ honour for Seema to be selected as a teacher trainer.

an

The correct option to fill in the blank is an.

The word "honour" is a noun, and it is not preceded by an article when it is used in the general sense of "respect or esteem." In the context of the sentence, it was an honour for Seema to be selected as a teacher trainer, meaning that it was a great privilege and responsibility.

The other options are not as appropriate.

• The is used to refer to a specific honour. This does not make sense in the context of the sentence, because there is no specific honour that is being referred to.
• No article is also grammatically correct, but it sounds a bit informal.
• An is used to refer to an honour that begins with a vowel sound. This is the most appropriate option because the word "honour" begins with a vowel sound.
• A is used to refer to an honour that begins with a consonant sound. This is not the most appropriate option because the word "honour" begins with a vowel sound.