The words scientists, separate projects, and contributions all indicate that there is a group of people under discussion in the sentence. The word including, then, is the most appropriate way to indicate Tesla’s participation in the group. Also, since the second clause of the sentence is subordinate, a comma is necessary before the conjunction.

1. Such indicates an example, not participation in a group.
2. Including is a subordinating conjunction and should be preceded by a comma rather than a semicolon.
3. The word including correctly indicates that Tesla was part of a group of scientists working on radio, and the comma before including correctly joins a subordinate to an independent clause.
4. The words not least among them being are redundant and unnecessary.
5. A semicolon is not correct in this sentence, and the word especially is inappropriate, given the context of Tesla being one among a number of scientists working on radio.

The correct answer is C.