serez parties vs serez sorties

Question

why is partir right ans sortir wrong pleas. i thought sortir is to go out so would be acceptable here, but isn'tis for same question as below, will you have left by 4 oclock

Cécile Janty-Davies · Accepted Answer

Hi Carol,
The verbs 'sortir' and 'partir' are often confused but they mean different things.

sortir= to go out / to come out
partir = to leave / to go

The actual Kwiz question was:
Vous ___ à quatre heures ? ( Will you have left at 4 o'clock ?)
So partir is correct here and not sortir. 
Hope this helps!

Jim Jones · Answer

Hi Carol,I haven't looked at the text, but the first thing that comes to my mind is the issue of transitivity.Partir does not take a direct object. Sortir can take a direct or indirect object depending upon whether used with avoir or être.Is this the key to your query?Jim