+0
Scenario: We just finished our exam and we are getting the marks back tomorrow. And I say:

Are these correct? Which one of these do I use? What do they mean?

1. You must be pretty dumb if you get a bad mark.

2. You must be pretty dumb if you got a bad mark. (What does this one mean compared to #1)

What if I add 'tomorrow' to it?

3. You must be pretty dumb if you get a bad mark tomorrow.

4. You must be pretty dumb if you got a bad mark tomorrow. (Incorrect with 'tomorrow' here?)

Scenario: I just finished an exam and my friend asks me how I did. I say:

Is only #7 correct

5. I did pretty good. I probably got a good mark.

6. I did pretty good. I probably get a good mark. (Is this sentence correct at all without 'will' ?)

7. I did pretty good. I'll probably get a good mark.

Thanks.
+0
#1 can be present or future tense. In this instance, it sounds as though the mark has not yet been received.

#2 is past tense. It sounds as though the marks have been received, but the speaker doesn't know whether the subject got a bad mark.

#4 is the wrong tense.

#5 and #7 are mostly correct. I think the preferred phrase is "I did pretty well."

#6 is missing the verb, it does need "will"
Comments  


1. You must be pretty dumb if you get a bad mark.

This is fine. It’s the first conditional: modal auxiliary verb + if + present simple

2. You must be pretty dumb if you got a bad mark.

This would work as the second conditional if you replaced ‘must’ with ‘would’. In such a case, the past simple ‘got’ would refer to the future, and such a form would suggest that getting a bad mark is unlikely, improbably or just simply imaginary.

As it stands, this sentence only makes sense if the papers have already been marked and, therefore, ‘got’ refers to the past. I’m unsure of the precise terminology but I think it’s also categorised as 'the first conditional' as we are referring to a condition that is possible even though it is in the past. If someone disputes the term being used for this form then please say so.

3. You must be pretty dumb if you get a bad mark tomorrow.

This is the same as number one.

4. You must be pretty dumb if you got a bad mark tomorrow.

Now, this doesn’t work as either the first conditional (‘got’ can’t refer to the past because of ‘tomorrow’) or the second conditional (‘must’ refers to a real possibility (a logical conclusion) whereas the past simple ‘got’ doesn’t).

If you replaced ‘must’ with ‘would’ then you would have the second conditional:

‘You would be pretty dumb if you got a bad mark tomorrow.’
 Vorpar's reply was promoted to an answer.