What is correct?

a -I am studying at the university of london?
b -I am studying at the london university ?

a - Once indoors , he immediately put off his wet clothes and dried himself.
b - Once indoors , he immediately took off his wet clothes and dried himself.

a- The children were told not to talk to strange people.
b- The children were told not to talk to strangers .

a- The day finished worst than it began.
b- The day finished worse than it began.

a- I'm sorry to cause you so much trouble.
b- I'm sorry to cause you so many trouble.

a- We all thought he was saying the truth.
b- We all thought he was telling the truth.

a- One of children wanted to go to the toilet.
b- One of children wanted to go to toilet.

a- The are hundreds of millions of stars in the space .
b- The are hundreds of millions of stars in space .

a- The television comapny receives most of its money from propaganda.
b- The television comapny receives most of its money from advertising.

a- I've been invited to a party .
b- I've been invited on a party .

a- The sun shines here everyday.
b- The sun shines here every day.

a- He's gone to buy a fresh bread.
b- He's gone to buy some fresh bread.

a- 'Hwllo , John . How are you ? ' very fine, thank you.
b- 'Hwllo , John . How are you ? ' fine, thank you.

a- It will not be long before scientists invent a cure for this terrible disease.
b- It will not be long before scientists discover cure for this terrible disease.