решить цепочку уравнений

FeS--->SO2 --->SO3--->H2SO4

Помогите с составлением уравнения!! 

Mg+P

K+P

Какова биологическая роль размножения?

Read the sentences and choose the right form of the verbs.

1. – We … a party tomorrow night. Come and stay with us.

a. have

b. are having

- How many people … ?

a. come

b. are coming

2. - What are your plans for tonight? Would you like to come over for dinner? - Sorry, I can't come. I … tennis tonight.

a. play

b. am playing

3. - Who … (you) … for?

a. do you wait

b. are you waiting

- My mother. She always … me at the station.

a. meets

b. is meeting

4. – Here is your ticket, sir. Your train … at 3.30.

a. leaves

b. is leaving

5. - Hurry up! The train … in a couple of minutes!

a. leaves

b. is leaving

Собрание сочинений из 4-х томов нужно поставить на полку по порядку. Вычислите вероятность того,что нужный порядок будет достигнут.