Answer: The right answer is the A) Life is an eternal struggle.
Explanation: Just to elaborate a little on the answer, it can be added that in these two lines the poet is describing life as a broad field of battle and as a bivouac, or temporary encampment, and this suggests struggle, difficulty, and discomfort. That imagery does not suggest that life is not worth living or that life is mostly unhappy and painful, however. Likewise, it does not mean that life is rarely problematic, but quite the opposite. Comparing life to a battlefield and to a precarious encampment suggests that it is indeed a constant struggle.