What is the difference between "might be" and "must be"? [closed]

(C ) 7 —You look worried. What's wrong?

—I can't find my wallet anywhere. It________lost.

A. must be
B. might be

Question:
Which one is right? A or B?

Solution 1:

Might be implies that there is a possibility it is lost. Must be lost states there is no other possibility.

If you can't find your wallet anywhere, it is lost:

lost adjective 1.1 Unable to be found.
_{Source: Lexico}

But if you must use a modal auxiliary verb, you'll have to choose A. must be; it's the modal we use for certainty—for deductions and conclusions:

I can't find my wallet anywhere. It must be lost.

That means that since you are unable to find your wallet, you have concluded that it is lost.

Or, as we say around here . . . No shit, Sherlock.