The correct option is C Whereas
All the options given are conjunctions. The sentence is comparing the workplace of one brother with that of the other. Contrasting conjunctions most commonly used are 'however' and 'whereas.' Between 'however' and 'whereas', 'however' is used at the start of a sentence to introduce a contrast with the previous sentence. 'Whereas' is used to contrast two ideas in the same sentence. Since the sentence is a single one, we must use ;whereas.' Hence, option C) Whereas is the right answer.