Step 1: Understand the meaning of INSCRUTABLE.
Inscrutable describes something or someone that is impossible or very difficult to understand, interpret, or read, such as an inscrutable expression or an inscrutable decision whose reasoning cannot be worked out.
Step 2: Find the opposite meaning.
The opposite of something that cannot be understood is something that can be understood. Comprehensible means capable of being understood or grasped clearly, which is the exact reverse of inscrutable.
Step 3: Eliminate the other options.
Confusing describes something that causes puzzlement, which actually sits on the same side as inscrutable rather than opposite it, so it is a near-synonym trap. Contradictory means self-conflicting or inconsistent, a different idea about logical consistency rather than about clarity of understanding. Contemptible means deserving scorn or disrespect, unrelated to how understandable something is. Corruptible means capable of being morally corrupted or bribed, also unrelated to comprehension.
Step 4: Conclusion.
Comprehensible, option (a), is the correct antonym of inscrutable.