1. Bill (write) his name.

2. He (learn) French for 5 years.

3. My friend and I (draw) a picture.

4. – Why are you so tired?

– I (play) football for two hours.

5. Mark (blow out) the light.

6. The kitten (drink) its milk.

7. Tom (work) in this company since 1999.

8. The tree (fall) across the road.

9. We (sell) this house since last month

10. They (look) for their dog since morning.

11. Her son (play) computer games since 5p.m.

12. We (clean) our flat all day long.

13. Jessica (talk) on the phone since early morning!

14. I (write) this verse for 5 minutes.

15. You (play not) football since you were 15 years old.

I would like to say a few words about mosquitoes. They are very nasty insects. They parasites on all living beings: people, animals. In Russia, mosquitoes are relatively harmless, although there is a huge number of them in Russia. But, in southern countries, in the tropics, mosquitoes are very dangerous. Their bite can kill a person. Theу are malarial mosquitoes...  The disease that they carry is called malaria. The mosquitoes breed on a warm time..
Mhe хотелось бы сказать несколько слов о комарах. Комары очень неприятные насекомые. Они паразитируют на всех живых существах: людях, животных. В России комары относительно безобидны, хотя их огромное количество в России. Но, в южных странах, в тропиках, комары очень опасны. Их укус может убить человека. Это малярийные комары.. болезни, которые они переносят называется малярией. Комары размножаются в теплое время...

We use these animals for different purposes. For example,  people often use dogs to looking for illegal substances (drugs). In ancient times, people used pigeons called   messenger-pigeon to exchange information. More often than not  we see dolphins water shows, this is really exciting!

People often used horses as means of transportation, and  , for example, the sheep give us   wool which we so need.

About the question "Could animals be used as secret agent?", I think it's impossible. Animals can't be used as  secret agent, because the exchange of information is impossible.