I will be leaving for Delhi tonight and . . . . . . . . to return by this week end.

The correct answer is: plan.

The other options are not correct because:

• waiting: This does not make sense in the context of the sentence. The speaker is not waiting to return to Delhi.
• likely: This does not make sense in the context of the sentence. The speaker is not saying that it is likely that they will return to Delhi.
• going: This is a possible answer, but it is not the most likely answer. The speaker is not simply going to Delhi. They are planning to return by the weekend.
• making: This does not make sense in the context of the sentence. The speaker is not making anything.

The speaker is saying that they are leaving for Delhi tonight and plan to return by the weekend. This means that they have made a plan to return to Delhi by the weekend. They are not simply going to Delhi. They have made a plan to return by a certain time.