Hi fab, Raja did a great job on corrections, but I just want to point out a couple more small things. (a couple are just other options)

No:7  We've walked for three quarters of an hour.

No:8  It's a play by Oscar Wilde, the famous playwright. (he is certainly famous in this neck of the woods!!!); (a small handy/useful saying for you!)

For No: 11, you could also have written: A/The cat is running after A/The mouse, the mouse is now going into A/The hole, and/but the cat can't catch it.

For No: 17, you could also have written: 

a) They came here by car

b) They often come by car

No: 20 Ben Nevis........Is located in the Scottish Highlands.

No: 21 Have you ever been to Loch Ness.

Hope these examples are useful.....Jo

Fabrizio: Bravo! Here are some corrections from an American point of view. In Britain, some of the specifics may be different, at times.

Exercises About Articles

complete these sentences with a/an when it's necessary

1- Patrick is a Catholic but his wife is a Protestant

1- Patrick is Catholic but his wife is Protestant  (Either)
2 - You mustn't use a pen or a pencil on a disk
3 - She works as a nurse in a hospital in central London
4 - A giraffe has got a long neck and a small ears
5 - What's a nice box of chocolates! and what's nice flowers
6 - It's quite an interesting book
7 - We've walked three quarters of an hour
8 - It's a play of Oscar Wilde, a/the famous playwright
9 - I don't feel very well. I've got a cold, or maybe a the flu
10 - He doesn't smoke cigars. He smokes a pipe

Complete with The when it's necessary

11 - A cat is running after a mouse. The mouse is now going into a hole, and the cat can't catch it
12 - Mary, are the children in the bathroom?
13 - Do you take milk in your tea?
14 - Can you pass me the salt, please?
15 - Can you play the violin?
16 - Have you ever seen the pope?
17 - They come here by car
18 - Look at the sky! It's so blue
19 - There were policemen everywhere
20 - Ben Nevis, the highest peak in Great Britain, is in the Highlands of Scotland
21 - Have you ever been to Lock Ness?
22 - Paris is the capital city of France
23 - The severn is the longest river in the U.K., but the most famous is the Thames.
24 - The English Plain is in the south
25 - There are some hills in England, which are called The Downs
26 - It's raining on the western coast
27 - The gulf stream is a warm current flowing in the Atlantic Ocean