Merge means to combine two or more things into one. For instance, two banks merged. It can also mean to blend or come together smoothly. As an example, consider merging traffic.
When one thing merges or is merged with another, they combine or come together to form one whole. Two things can also be said to merge or be merged.
The verb merge means to join something together seamlessly. For example, when merging onto the highway, you must join the traffic smoothly, forgetting everything you learned on the bumper cars at the fair.
When two or more things combine to form one, they merge. If your favorite deli, The Cheese Stop, merges with a sandwich shop called Chez Lui, the two establishments' names may also be merged, becoming Chez Cheese. When things appear to blend, you can also use merge. When the words in your book start to blend together, you know it's time to sleep.
Thus this is the meaning of merge and hence we can conclude that the correct answer would be Option d.