Select the correct passive form of the given sentence.

They welcomed Jane and Karan to the gathering.

Jane and Karan were welcomed by them to the gathering.

The correct passive form of the given sentence is Jane and Karan were welcomed by them to the gathering.

The active voice of the sentence is "They welcomed Jane and Karan to the gathering." This sentence is in the simple past tense, which is used to describe an action that happened in the past. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "they" and the main verb is "welcome." The past participle of "welcome" is "welcomed." So, the passive form of the sentence is "Jane and Karan were welcomed by them to the gathering."

The other options are incorrect because:

• Jane and Karan is welcomed by them to the gathering." This sentence is in the simple present tense, but the verb is in the passive voice. The verb should be in the past tense to match the tense of the rest of the sentence.
• Jane and Karan had been welcomed by them to the gathering." This sentence is in the past perfect tense, which is used to describe an action that happened in the past before another action happened. However, there is no other action mentioned in the sentence.
• Jane and Karan are welcomed by them to the gathering." This sentence is in the present continuous tense, which is used to describe an action that is happening now but is not finished. However, the action of welcoming Jane and Karan to the gathering has already happened.