I need your help. Which one of these two sentences is more accurate?
1. Extreme rain can cause the river to flood the city
1. Extreme rain could cause the river to flood the city
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Both sentences are grammatically correct but they have different senses.
"Extreme rain could cause the river to flood the city".
In the sentence the auxiliary verb "could" conveys two senses as follows:
Could is the past of can. The sentence means that it was possible or likely that extreme rain might cause the river to flood the city.
Could is also used to express possibility in the present and future. Here it means it's possible that extreme rain may cause the river to flood the city.
"Extreme rain can cause the the river to flood the city".
We can use "can" to express a general fact i.e. something that usually, but not always, happens. Extreme rain usually, not always, causes the river to flood the city.