The presence of HOWEVER indicates that the previous statement was a counter premise and what will follow is the main conclusion.

Option A - Incorrect
To undermine means to go against a claim. However, the reverse is the case in the bold sentence.

Option B - Incorrect
The bold statement does not point out any point of disagreement, therefore, it's in lieu of option A.
The bold statement in the question supports the claim and not otherwise.

Option C - Incorrect
The stated/bold sentence is not a repetition of the initial statement. It is, however, a point of making the argument that specifies a point that has not been previously stated.

Option D - correct
Yes! The bold statement is a backup statement to validates the writer's opinion. Clearly logical and valid.

Option E - Incorrect
Not the final destination, as some other points were still reached. This makes the sentence incorrect.