Select the correct active form of the given sentence.
The test flight of Gaganyan was successfully carried out by the scientists of ISRO.

Correct option is B

The correct active form is "The scientists of ISRO successfully carried out the test flight of Gaganyan."
In the original sentence, "The test flight of Gaganyan was successfully carried out by the scientists of ISRO," the passive voice is used.
In converting to active voice, the agent (the scientists of ISRO) becomes the subject of the sentence, and the action (carried out) follows directly.
The sentence structure in option (b) correctly positions the subject first, followed by the verb and the object (the test flight of Gaganyan), while also maintaining the past tense as in the original sentence.
Rule of conversion:
Subject + V2 + object. -> <- Object + auxiliary verb (was, were) + past participle + by + subject.