Your pen-friend Ann wrote you a letter:​

When choosing a future career, we should consider different factors. In my opinion, money is one of the most important factors when you make a choice. There are highly paid jobs and low-paid jobs. For example, a businessman, a president or a film star, are highly paid jobs. A worker, a doctor or an engineer, are low-paid jobs. I think everybody wants to earn as much money as possible. Training, promotional prospects and conditions should be also taken into account.That's why I want to be a director.On the other hand, it's good when you get satisfaction from your job. It is very important to choose a profession that suits your interests. In my opinion, a job should be interesting and socially important.

1. He always comeS to his work in time.
a) –s Это показатель 3-го лица единственного лица глагола в Present Indefinite; 2. We had dinner at our friend’s. c)-s - Это показатель притяжательного падежа имени существительного
3. I write to my parents very often.
b) –s - Это Признак множественного числа имени существительного
4. My sister haS a very cozy house.
a) –s  Это показатель 3-го лица единственного лица глагола в Present Indefinite; 
5. My mother has two sisters.
b) –s - Это Признак множественного числа имени существительного