
Answer:
1) "I am going to explain why many couples in Russia are choosing to live together rather  than get married."
Explanation:
1 I am going to explain why many couples in Russia are choosing to live together rather  than get married.
   [] Good! It gives an intro, but doesn't give away the whole essay.
2 Even though marriage is a strong and respected institution in Russia, more and more  people are choosing to live together before marriage, despite the cultural pressures.
   [] Isn't a thesis as it is directly announcing the topic.
3 Marriage in Russia.
   [] Has no background and is missing parts.
Have a nice day!
 I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly. (ノ^∇^)
- Heather