Write present, present participle, past or past participle to identify the form of the underlined verb.

Question

I need to know first what is present participle and what is past participle?
1. Machines existed in Leonardo's day. Existed is underlined so I am saying this is just past.
2. For example, waterwheels turned millstones. Turned is underlined-past
3. As a boy, Leonardo had watched machines closely. Had watched is underlined. I don't know if this is just past or past participle.
4. By adulthood, he had analyzed how each part worked. Had analyzed is underlined and I am confused on this one.
5. Unlike others, Leonardo combined parts in new ways. Combined is underlined and this is past
6. He thought, Aha! This change improves the machine. -present
7. He reasoned, "This invention is working better with different parts."-present participle
8. He explained his analyses in journals. Explained is underlined and this is past
9. Grateful engineers still study his sketches. Study is underlined and this is present
10. These illustrations are serving as blueprints for us. Are serving is underlined but I am confused on the answer.

Please look this over and let me know the ones I have wrong and how to figure out the correct answer.

Answer 1

Please study this site to learn about participles.

http://www.chompchomp.com/terms/participle.htm

These answers are correct:
1, 2, 5, 8, 9

6., 7. What is underlined?

Answer 2

6. The word improves is underlined
7. Is working is underlined

Answer 3

Thanks. 6 and 7 are right.

Answer 4

So would 3 and 4 then be past participle.

Answer 5

Yes. 3 and 4 use the past participle.