C - A library, online labrary databases, careful and evlauative internet serces, old newpapers, magazines and periodical publications are the BEST places to go and find resources.
The sentence that has a verb in the active voice is B. Guglielmo Marconi perfected a type of radio technology.
The rest of the sentences have their verbs in the passive voice. If you wanted to make a passive sentence out of B, you would say - A type of radio technology was perfected by Gugliermo Marconi.
