Translation:That cat was sleeping when we arrived.
The English is wrong. The sentence needs a place or location for "come"
Ex: ... when we come back / ... when we come in / ... when we come home.
The english translation here is terrible. It should be "the cat was sleeping when we arrived". Or, "the cat was asleep on our arrival. I have to assume this is due to using american english grammar which is very different from english (England) grammar proper and for learning purposes.
i wrote "The cat was asleep when we arrived"......but alas was marked wrong. how does one differentiate "slept" and "was asleep"
Even in English they are different. "Asleep" is an adjective. "Sleep/slept" is a verb. Description vs action.
how can you tell present tense from past tense? ex: that cat sleeps or. that cat was sleeping I wrote that cat sleeps when we arrive
There is no difference, past/present/future tense, it's all the same in Indonesian.
The verb is not conjugated for tenses/plural/singular, the verb remains the same, there is no change in form.
Your translation "that cat sleeps when we arrive" is one of the accepted translations.