On a careful reading of the sentences, we get a fair idea of the content being conveyed. The single compound sentence so formed should be grammatically correct, conveying a similar meaning.

Let us check the options one by one.

Option 1 : This is incorrect because of the disruptive flow of the sentences. The use of because of  twice in the sentence is unnecessary. Instead, the sentence could have been improved by using the phrase ‘because of the fact that with only around 44 branches, their standalone net profits are of Rs 34 billion in FY’2018’.

Option 2 : The use of although is done to convey a surprising or contrasting element. It has been misplaced in the sentence. Citibank India’s operations are significant as their standalone net profits are of Rs. 34 billion in FY’2018. The surprise lies in the fact that they have only 44 branches.  So, we can eliminate this option.

Option 3 : This makes logical sense. The use of even though is done appropriately to highlight the fact that with only 44 branches, Citibank India managed to have standalone net profits of Rs 34 billion in FY’18.

Option 4 : The use of nonetheless is not required as we have already used even though in the first part of the sentence.  Either ‘Even though it has only around 44 branches, Citibank India’s operations in India are significant as they made standalone net profits of Rs 34 billion in FY’2018’ or ‘With only around 44 branches, Citibank India’s operations in India are nonetheless significant as they made standalone net profits of Rs 34 billion in FY’2018’ would have been a meaningful sentence.

Therefore, the correct answer is option 3.