Select the correct passive form of the given sentence.
"He is solving a complex problem."

Correct option is B

The correct passive voice of the given sentence is (b) A complex problem is being solved by him.
Rules of conversion (Present Continuous):
· Identify tense: is solving → Present Continuous (am/is/are + V₁-ing).
· Passive structure for Present Continuous: am/is/are + being + V₃ (past participle).
· Move the object to subject position and add “by + agent” if needed.
· Structure:
· Active: Subject + am/is/are + V-ing + Object.
· Passive: Object + am/is/are + being + V₃ + (by + Subject).
· Application: He (S) + is solving (V) + a complex problem (O) → A complex problem is being solved (by him).
· Examples:
· They are building a bridge → A bridge is being built.
· She is writing a letter → A letter is being written.
· Why other options are incorrect:
· (a) lacks the continuous marker “being.”
· (c) incorrect tense/structure (“has solved” needs an agent-subject and an object; also would be has been solved in passive).
· (d) past perfect without passive auxiliary (had been solved would be needed).