If I fall ill, I will stay home.

如果我病了，我会待在家里。

youdao

If I fall ill, I'll see my doctor.

如果生病了，我会去看大夫。

youdao

What if I fall ill while I'm away on holiday?

如果我在放假时生病了怎么办？

youdao

I wonder if I will fall.

我担心我会不会跌倒。

I wonder if 实战 - SpeakingMax英语口语达人

The native structure is this double stranded structure here and if I heat it up slightly and I add some base, so under slightly basic conditions, these molecules will fall apart because you've created conditions where the hydrogen bonding is no longer favorable so they peel apart.

原始结构,在这里就是指DNA双链,如果我稍微加热,并且加入一些碱,在弱碱性的条件下,这些配对碱基会分开,这是因为在一定条件下,碱基对之间的氢键,不再稳定并且会断裂分开

耶鲁公开课 - 生物医学工程探索课程节选

But if I fall asleep and the microphone hits the floor, just cut me off.

NPR: Mexico Awaits Outcome of Tight Presidential Vote

If I can fall off one cliff, I should be able to fall off each cliff.

FORBES: [Spoilers spoilers everywhere...]

If I did fall on my face, I am obviously still concussed and dreaming.

BBC: The trainee