Thank you for the help! I have one more question on grammar.
QU: What is the mistake in this sentence, and how would you explain the mistake?
"Why didn't you answer the telephone? Because I had a bath?"
I see that the mistake is "I had." It should be "I was having." Would I be right in saying that this is because "I had" refers to an event that could have occurred any time in the past but "I was having" implies that the person was in the bath at the time of the phone call?