I believe it would be D I may be wrong
The correct answer should be additionally.
The word additionally would provide the best transition between these two sentence. It is so because you have one idea in the first sentence, and then you want to show another idea very similar to the first one in the second sentence. Using additionally to convey that is the way to go.
Answer:
one: know what the whole project is about i.e that's know if it's educational,talking business contemporary issues etc
two: check for topics in the internet.
three : when that's done, you check on recent videos on the topic
the answer is a. creates a lonely feeling.
