—Will you give me a hand? I have some trouble_______ the scientific problem.

—Don't worry. I'll try my best to help you _______.

A．solving; in five minutes

B．to solve; in five-minute

C．to solve; after five minutes

D．solving; after five-minutes

最先用实验的方法证明了空气成分的科学家是______；空气中含量最多的物质是______；最简单的有机物是______；人体中含量最多的金属元素与地壳中含量最多的非金属元素形成的化合物的化学式为______．