Dear Wooshky2, "He" is the subject, "heard " is the verb. What did he hear? A dog? Or barking? It seems to me he heard both--a dog barking. Even though I cannot explain it, hearing a barking dog and hearing a dog barking are two different things. The "barking dog" focuses on a characteristic of the dog; by nature it is a yapper. The "dog barking" focuses on the activity of the dog and where that activity takes place. If you say "barking dog", barking is an adjective. When you say dog barking, "barking outside the window" is a verbal phrase with "dog" as its subject. The helping verb "was" has been left out because our sentence's main verb is "heard" and we have combined two sentences in one thought. The two sentences were "He heard a dog" and "the dog was barking outside his window." Same is true for the second sentence. That was an excellent question! You really made me think and scratch my head for awhile. For sentence 3, it depends on the meaning. If eight hours ago he ate the hotdogs, simple past should be used. But if eight hours ago his eating of the hotdogs had already been accomplished, then you need the past perfect. The first sentence seems to imply that all his eating stopped eight hours ago, which would make the perfect (finished) tense the better choice. Hope this helps!
