Select the option that expresses the given sentence in Direct to Indirect Speech.
He said, "It must be raining outside."

Correct option is B

The correct indirect speech is (b).
Explanation: The modal must here expresses a logical deduction/strong inference (not obligation). In reported speech, must generally remains unchanged when it conveys deduction. So: He said (that) it must be raining outside.
· (a) should weakens the force and changes meaning.
· (c) might reduces certainty from strong inference to mere possibility.
· (d) had to be treats must as obligation, which is incorrect in this context.
Rules of conversion (summary):
1. Remove quotation marks and, optionally, add that.
2. Keep pronouns/time words consistent.
3. Modals in reported speech:
· must (deduction) → must (unchanged).
· must (obligation) → often had to.
· may → might (often backshifted), can → * could, etc., depending on sense.
Structure:
· Direct: He said, “It must be raining outside.”
· Indirect: He said (that) it must be raining outside.
Extra tip: If the deduction refers to a completed past event, we may render it as must have + V3: He said (that) it must have been raining.