Why did you join the club? (question mark)
She knew that. (period)
Biology is the study of life. (period)
Is the concert on Friday or Saturday? (question mark)
Stop that immediately! or . (exclamation mark or period)
That is ridiculous! or . (exclamation mark or period)
When are you stopping by again? (question mark)
The forecast is for rain all afternoon. (period)
We use question marks at the end of sentences that as a question. These sentences will likely start with who, what, when, where, why, how, or do. A sentence that simply states a statement will end in a period. We can use exclamation points when we want to emphasize something. They would be appropriate in a couple sentences, but you could also simply use a period. They are both correct.
