Step 1: Understand the meaning of "Inscrutable."
"Inscrutable" means something that is difficult or impossible to understand.
Step 2: Analyze the options.
"Comprehensible" means something that is easy to understand, making it the antonym of "inscrutable."
"Mysterious," "Opaque," and "Obscure" all relate to something difficult to understand or hidden, which are synonyms of "inscrutable."
Step 3: Conclusion.
The antonym of "inscrutable" is "comprehensible." Thus, the correct answer is: \[ \boxed{{Comprehensible}}. \]