Select the correct option:
Her interpretation was diametrically ________ to the accepted doctrine.

The correct option is opposed.

Explanation:
The phrase "diametrically opposed" is a common English idiom and collocation meaning completely, directly, or 100% opposite to something.

Let's analyze the meanings of the given options to understand why opposed is the correct choice:

1. Opposed: Completely different or contrary to something (e.g., opinions, doctrines, beliefs). When combined with "diametrically", it means facing directly opposite, like two points on opposite sides of a circle's diameter.
2. Adverse: Harmful, unfavorable, or hostile (e.g., adverse weather conditions, adverse reactions). It does not collocate with "diametrically" in this context.
3. Averse: Having a strong dislike or opposition to something (e.g., risk-averse, averse to hard work). It is typically used for feelings or attitudes of people rather than doctrines/interpretations.
4. Inverse: Reversed in position, order, or relation, usually used in mathematical, technical, or quantitative contexts (e.g., inverse proportion).

Therefore, the word that correctly completes the sentence to express complete opposition to the accepted doctrine is opposed.