Choose the correct negative sentence in present perfect.

His mother has so far not made dinner.
His mother has not made dinner so far.
His mother have not made dinner so far.

They have not learned the formulas, so they will probably fail the test.
They has not learned the formulas, so they will probably fail the test.
They have not learn the formulas, so they will probably fail the test.

Dear Anton,
My summer holidays were very interesting. I spent them guess where.I visited London!. This is really a great city with its old cathedrals, churches, palaces and museums . I took a lot of pictures of London. Most of all I enjoyed going on а river trip down the Thames. We saw the Houses of Parliament along the north bank of the Thames. The clock tower of the Houses of Parliament is famous for its big hour bell known as «Big Ben». We saw the Tower of London near Tower Bridge. 
We also visited  the British Museum and Buckingham Palace where the Queen lives.  We were lucky to make a ride on the London Eye wheel and  went to Trafalgar Square where a tall Nelson's coloumn stands. I enjoyed doing the sights very much. That's all for now.
Best wishes,
Sasha

1. The doctor said, "The child is very ill. He must be taken to the hospital at once." 2. A man should help his parents when they become old. 3. There are no buses or taxis, so we have to walk. 4. Everybody should learn a foreign language. 5. We can't live without food and water. We must eat and drink. 6. I have to get up early tomorrow, so I must go to bed late tonight. 7. You can't drive a car at night without lights. 8. Man can't live by bread alone. 9. The matter is to be discussed in tomorrow's debate. 10. You shouldn't sit there in your wet clothes; you will catch cold it you do. 11. They needn't do all the exercises; it will be sufficient if they do four of them.