I wouldn't do that. I'd speak to the teacher first and see what she says.

But if we don't make those investments, we'll risk loosing market share.

Don't get me wrong, I just think we should look at some other options before making a decision.

Even so, if we change classes this late, we might not get a passing grade.

Don't forget that you still need to finish all your homework BEFORE you can do that.

Very true, but we still need to get the garden in shape before building a new deck.

Sometimes we disagree with what a person says. So that we do not seem to be impolite, we can start our disagreement with a phrase that is gentle and friendly. Here are some examples. Try to use them in your own conversations.