1 Is he the politician that / which helped all those people? 2 My city, that / which has over four million inhabitants, is very polluted,
3 John's colleagues, who/ that he'd worked with for five years, gave him a big leaving party,
4 It was her personality that / who I disliked so much
5 Our heath service employs 1,7 million people, that / which makes it the biggest employer in the UK.

1. The traffic is heavy today. Leave home earlier.
2. We liked the hotel. We advise you to stay there.
3. Last year we participated in an international conference on globalization.
4. In the center of the City there is the London Stock Exchange, where daily transactions are made to purchase and sell millions of shares and securities.
5. I usually walk to work, but it's raining today, so I'm going by bus.
6. Where is my report? I have just taken it to to be typed.
7. If you agree to our terms and conditions, we will give you a discount.

I'm sitting in an armchir tied up tightly with belts. Dawn light shines in my eyes through a little window in front of me. One rapid inpulse and I'm into open space in a metter of seconds. The view in a window is just... white, i can see nothing there. Oh, wait, actually i see everything. After we've reached the speed of light for us here stars turned into stains. I'm one of the first who can experience that phenomena. Estonishing...
  Will I ever come back? I don't know. I don't need to live anymore, I've seen everything.