Hello. You did not submit the sentences to which your question relates, which makes it impossible for that question to be answered. However, I will try to help you in the best possible way.
Conditional sentences are sentences that have a condition that can happen as a result of another condition. This type of sentence is classified as "first conditional" when it presents particular situations that can happen in the real world, regardless of whether it is in the past, present or future.
In a way that cannot be controlled
It would be A.
The incorrect contraction in that sentence is it's. It's is a contraction for it is, so it basically means : They're following the creek to it is source. This doesn't make sense. So, you would replace it with the other form, which is its. Its shows possession.
Hope this helps!
