Complex sentence: When B is to be executed, of course he only can answer with C (case 3 and 4), likewise when C is to die, the answer is B (case 5 and 6).
Split into simpler sentences: When B is to be executed, of course he only can answer with C (case 3 and 4). Likewise, when C is to die, the answer is B (case 5 and 6).