At a/the __ level or At __level . Article or not? If yes which one (a or the)?

Solution 1:

In your examples, I would use "the". But in other cases I might use no or the indefinite article, for example,

It was a smoggy day. Pollution made the air at ground level almost unbreathable.

It's an understatement to say that Labron James plays basketball at a high level.

It depends on whether the adjective you're using is chosen from an implied set, in which case you're specifying a particular level from some set of levels the audience knows about, and the definite article is appropriate. Or if the adjective is simply descriptive, in which case no article or the indefinite is appropriate.