Hi みゆ :) I think the first option in each sentence is the correct one. because I have never seen a sentence with the same structure as the second ones. if you want to use "which" or "who", you can use it as follows: the cat, which is standing on the car, .... the forty students, who were waiting in the room, .... Sorry If this is not your question, my Japanese is still very bad. P.D: にほんごをべんきょうします If you like, we can make a languague interchange.

There's no difference between the two sentences in each example. The second sentence called "reduced relative clause" which means relative pronoun (who, which, that) removed and replaced with a participle (V-ing). You can use "reduced relative clause" with all types of tenses. You may read this page if you want for more examples: http://users.utu.fi/micnel/shortclauses.htm I hope this helps :)

上の文は、現在分詞の形容詞的用法ですよね、どちらも意味は全く同じですが、現在分詞を使うほうが、柔らかい、くだけた表現になると思います。which isと言わなくても済むわけですから。 日本語でも、同じことを言うのに、短いほうが、くだけた言い方になりますよね

i can help you in English. will you help me in improving my japanese??? if yes just tell me how can I contact you