英语语法分析

They saw a footmark in the sand.

他们发现沙地上有脚印。

I haven't find my father's footmark even now.

即使到了今天，我还没找到爸爸当年的足迹。

He studies footmark for a whole life, it is our country's famous footmark expert.

他毕生研究足迹，是我国闻名的足迹专家。