Answer:

The correct option is (b) finishes.

Explanation:

The given sentence is in the present tense and it talks about a future event. So, we need to use the present simple tense in the subordinate clause and the future tense in the main clause.

The correct sentence would be:

After Manisha finishes her studies, she plans to work in her father's firm.

Let's see the explanation in detail:

1. Use of 'After':
The sentence starts with 'After', which is a subordinating conjunction. It is used to show the relationship between two events in time. The event that happens first is in the subordinate clause and the event that happens second is in the main clause.

2. Use of 'finishes':
The verb 'finishes' is in the present simple tense, which is used to talk about habits, routines, and facts. In this case, we are talking about a future event, but we use the present simple tense to talk about it because it is a fact that Manisha will finish her studies.

3. Use of 'plans':
The verb 'plans' is in the present tense because it is a future plan. We use the present tense to talk about future plans and arrangements.

4. Use of 'will':
We do not need to use 'will' in this sentence because we have already indicated the future event with the word 'after'. However, we could rephrase the sentence to include 'will' in the main clause:

Manisha will work in her father's firm after she finishes her studies.

This sentence has the same meaning as the original sentence.

Finishes