"Inscrutable" describes something impossible to understand or interpret, mysterious and hard to read, such as an inscrutable expression on someone's face. This question asks for the word most opposite in meaning.
Since inscrutable means impossible to understand, its true opposite is a word that means easy to understand, which is "Comprehensible."
Let's summarize:
So the correct answer is "Comprehensible."
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?