Question

i (smell) something burning.correct tense

Answer 1

You can use any tense here, past or present, it'll still work for both and be relevant:

I smell something burn.

I smelt something burning.


Both are correct.



Note: in conversation, we (if not you, I definitely) often say "I smell something burn"
Since you smell the burning odor at one instance, you have to use the continuous for of the verb BURN, that is Burning, because if you use I SMELL SOMETHING BURN - it'll be grammatically incorrect, just to clarify!

Answer 2

Answer:

we ......... for his call since for time 20 ( wait) tense