Explanation:

Correct answer is (b). The given statements seem to be effects of a common cause.Applying the elimination technique, let’s check the relevance of each of the options one by one.
Possibility 1.
On account of technological change that banks in India have embraced, the onus is on them to integrate inter-generational legacy systems across branches, ATMs and online banking networks into one seamless and secure whole. We can observe here that though the formation above is grammatically correct, it doesn’t express a meaningful context. This hence eliminates option C.
Possibility 2.
Besides the onus on banks to integrate integrate inter-generational legacy systems across branches, ATMs and online banking networks into one seamless and secure whole, they in India have embraced technological change. Once again we have here a construction that is grammatically correct but logically flawed. This hence eliminates option A and D as well.
Possibility 3.
With banks in India having embraced technological change, the onus is on them to integrate inter-generational legacy systems across branches, ATMs and online banking networks into one seamless and secure whole. Clearly, the synthesis made above is both grammatically and contextually correct and keeps the flow of the sentence intact.
Option B is hence the correct answer