I didn't drink the polluted water from the river or I ( might become - might have become ) ill now. And tell me why.

I honestly don’t like this sentence as a whole. The sentence itself isn’t grammatically incorrect, but the sentence sounds incredibly awkward. I would’ve written it as “I didn’t drink from the river’s polluted water as it could have (or would have) caused me to become ill.” I just feel like the sentence could be structured better.

Maybe I’m weird, but I’d say: “I didn’t drink the polluted water from the river, or I’d have (I would have) become ill by now” “I didn’t drink the polluted water from the river, or I’d’ve (! I would have) become ill by now.” “I didn’t drink the polluted water from the river, or else/otherwise I’d have (I would have) gotten sick by now” These are the kind of things my brain would naturally say for the sentence you provided

"I didn't drink the polluted water from the river because it might have made me ill." "I didn't drink the polluted water from the river" is a full statement, but it is disconnected from the "I might have become ill." If we're thinking the river is what could have made you ill, then that needs to be clarified. You wouldn't have become ill for no reason- the water would have caused the hypothetical illness. The consequence would be caused by the water, so the subject (the noun doing the verb) and object (the noun on the recieving end of the verb) flip in the second half of the sentence. Using the word "now" at the end of your sentence is unnecessary because you're speaking from the present, and the consequence of past actions would already be implied to have been taking place now. You could also use "otherwise" instead of "or" for the sentence to make more sense. "I avoided drinking the polluted water from the river, otherwise it might have made me ill." Here, "otherwise" is specifically referring to an alternate situation or choice that didn't happen, which fits your sentence. Another option is adding the word "else" behind "or" to make the common idiom "or else," expressing consequences if an action is not taken. Examples of similar sentences: "I have to be well rested to drive, otherwise I might fall asleep at the wheel." "I didn't pick up the snake, because it might've bitten me if I had." "I need to stay with the baby while he's napping, or else he might wake up and fall off of the bed." Note: "The polluted water from the river" is technically correct, but it's also a mouthful and sounds slightly unnatural. "The polluted river water" would be a more natural way to talk about the water.

This sentence is garbage. The word "or" has no place in the sentence.

It seems to me that you need to use the third conditional: If I had drunk the polluted water from the river, I might have become ill. Or you could use the word "otherwise": I didn't drink the polluted water from the water. Otherwise, I might have become sick.

It should be “might be” because it’s happening now. The whole sentence should be “Fortunately I didn’t drink the polluted river water or I’d be ill now” in native English.

I didn’t drink the polluted water from the river *because* I might have become ill (no now). …from the river. I might become ill, *if I had*. …from the river. I might have become ill, *if I had*.

I didn't drink the polluted water from the river *because it might have made me ill*.

I agree with your two alternatives. I think "... might have become ill *by* now" would be a third alternative

It sounds weird because it says “or” instead of “because” and also the word “now” shouldn’t be there. “I didn’t drink the water because I might have become ill”

I would say "I didn't drink the water because it might have made me sick". "I might have become ill" works but it sounds unnatural to me.

The latter is correct, but the whole think is unnatural—I'd say "I didn't drink the polluted water from the river or I would've gotten sick".

Might have become is correct. Might become is future, might have is past

Yeah, the sentence sounds a bit off. I'd add a "I'm glad" at the start. I'm glad I didn't drink the polluted water from the river or I might have become ill now.

“Might have become” is correct. > I didn’t drink the polluted water from the river, or I might have become ill now. “Now” can refer more broadly to the present time or circumstance, not just the exact current moment. This is more or less equivalent to: > I didn’t drink the polluted water from the river, or I might have become ill recently.

“Might have become” is the right answer as the other commenter stated, but I also think this sentence is really weirdly phrased. “I didn’t… or I might have …. now” is an odd structure that I don’t think many native speakers would use; a more natural phrasing would be “It’s a good thing I didn’t drink the polluted water from the river, or I might have become ill by now.”

Become -> (past participle) Therefore, it should be completed with “have”, this answers it’s the second option. *Why can’t it be the first anyway?* Well because bringing up a consequence (action) made and already finished with only might won’t work out, it’s like saying “I might failed on the exam because I skipped class today”