Question

Identify whether the bold term is an abstract or concrete noun. the notion that he should be promoted is ridiculous.

Answer 1

I think that the bold term is considered as an abstract noun.
A concrete noun should be seen, touch or smelt. So from the statement about, a notion is a form of idea. This will conclude that it couldn't be seen, touch, or smell from our senses unlike any physical object. So the answer is an abstract noun.

Answer 2

the notion that he should be promoted is ridiculous.

I believe the bold term is considered as an abstract noun.

The characteristic of a concrete noun is it could be seen, touch or smelt. Since notion is a form of idea, it couldn't be seen, touch, or smelt like any physical object, so we could considered it as an abstract noun.