The correct option is C cause
The word that fits in both the sentences is option C, cause. Cause means origin or the reason why something happens. Cause also means a socially valued principle, like we say social cause. The context of sentence I is that he could not give any reason why he behaved that way. And second sentence means that a man must live, struggle and die for a cause. Option A 'target' is the aim of an attack. Option B 'Goal' means objective or intention. These two options A and B do not fit in sentence II. Option D 'purpose' means motive or reason. Option E 'explanation' means clarification. These two options D and E do not fit in sentence II. Thus, the best fit for both the sentences is option C 'cause.'