Only then did he ________ the situation he and his fellow soldiers were in.
句意：只有到了那个时候，他才意识到他和他的士兵们现在的情况。be aware of为固定搭配，意为“认识到，意识到”。B、D两项缺少介词of。A项缺少系动词，因此排除。正确答案为C。