Ответ:
1) Let's take the <u>first</u> train
2) Have you met <u>Oleg's</u> friend there
3) The region is well known for <u>it's</u> natural resources
4) No one likes her. She talks about <u>her</u> all the time
5) She talks about <u>her</u> son all the time
6) What have that <u>woman</u> told you?
7) I've made some cheese <u>sandwiches</u>
8) <u>These</u> ponies are funny
9) The new swimming pool is much <u>bigger</u> than the old one
10) Here's my <u>parents</u> address
11) I think her photos are better than <u>Sam's</u>
12) Don't help <u>her</u>. She can do it <u>herself</u>
13) Before <u>we</u> begin the discussion, let's introduce <u>us</u>
14) You'll get the chance to test <u>yourself</u>
15) You'll get the chance to test <u>them</u>