Mmm... yummy yummy...
would "lots of cats" be correct here?
(just "......cats are eating" (no THE) was marked wrong.)
Is "At the moment" a preposition?
Is there a rule for placement of prepositions?
Is it always (something like): Prep + Obj + Verb ?
or could I say: "nhũng con mèo đang ăn vào lúc này" ?
yes you can say "những con mèo đang ăn vào lúc này".
Can I also use các instead of những? What is the difference between những and các ?
Sorry I left a loose comment while trying to answer your question. Các and những are interchangeable.