I was sleeping that time. or I was sleeping at that time.
I am wondering which one is correct expression. I'd appreciate if some tells me.
"sleeping at that time" - At that specific time of day
"sleeping that time" - This refers to a specific event or a specific instance.
I didn't answer your call because I was sleeping at that time. You called at two AM on Tuesday!
I should've answered that inquiry immediately. Now my competition might get this account. I sure was sleeping that time. My only chance now might be to come in at a lower price.