Every success and failure to an individual’s growth and maturity.
A. contribute B. is being contributes
C. contributes D. have been contributed

1  If my friend comes to see me, I will be very glad.
If my friend came to see me, I would be very glad.
If my friend had come to see me, I would have been very glad.

2  If mother buys a cake, we will have a very nice tea party.
If mother bought a cake, we would have a very nice tea party.
If mother had bought a cake, we would have had a very nice tea party.

3  If we receive a telegram from him, we will not worry.
If we received a telegram from him, we wouldn't worry.
If we had received a telegram from him, we would not have worried.

4  If you don't work systematically, you will fail the examinations.
If you didn't work systematically, you would fail the examinations.
If you hadn't worked systemtically, you would not have failed the examinations.

5  If you are busy, I will leave you alone.
If you were busy, I would leave you alone.
If you had been busy, I would have left you alone.

6  If I live in Moscow, I will visit the Tretyakov Gallery every year.
If I lived in Mocsow, I would visit the Tretyakov Gallery every year.
If I had lived in Moscow, I would have visited the Tretyakov Gallery every year.

7  If I get a ticket, I will go to the Philharmonic.
If I got a ticket, I would go to the Philharmonic.
If I had got a ticket, I would have gone to the Philharmonic.

8  If I live near a wood, I will gather a lot of mushrooms.
If I lived near a wood, I would gather a lot of mushrooms.
If I had lived near a wood, I would have gathered a lot of mushrooms.

9  If my father returns early, we will watch TV together.
If my father returned early, we would watch TV together.
If my father had returned early, we would have watched TV together.

10  If she knows English, she will try to enter the university.
If she knew English, she would try to enter the university.
If she had known English, she would have tried to enter the university.

Hi! I'm on holiday in London. I (am staying) with my friend, Jane.
She (lives) in the centre of London, near Hyde Park.
I (have been) here since Saturday and I (have already done) lots of things. I have visited) the Tower of London, the British Museum and Madam Tussaud's.
I (went) to Madam Tussaud's on Monday. It (was) terrible. When I (entered) the Chamber of Horrors, I (screamed).
Yesterday Jane and I (went) shopping. I (wanted) to buy some souvenirs. But while I (was paying) for a T-shirt, someone (stole) my bag. Luckily, I (had already spent) nearly all my money.
There (are) a lot of things I (have not done) yet. I (haven't been) on a boat trip down the Thames yet, I (haven't seen) the Millennium Dome.
If the weather (is) fine tomorrow, I (will go) on a boat trip. I hope Jane (will be able to) keep me company.
I (like) London very much. I (have never seen) such a beautiful city. You (must) visit it some day.