Which one is the correct spelling?

1.Fill in each blank with the most appropriate word/words. The idiom 'Let the cat out of the $bag^{\prime} means$ –––.

2.Fill in each blank with the most appropriate word/words. He said he had left the parcel ––– the chair ––– the window.

3.Fill in each blank with the most appropriate word/words. Scientists have discovered a liquid which boils at about 165°C with ––– decomposition.

4.Fill in each blank with the most appropriate word/words. What does global warming have ––– overpopulation?

5.A strict vegetarian ––––.

6.Fill in each blank with the most appropriate word/words. Please let me know why ––– the class.

7.Fill in each blank with the most appropriate word/words. The future of the planet doesn't look so good, but there isn't much –––.

8.Fill in each blank with the most appropriate word/words. The fact that some birds fly hundreds of miles to ––– without ever having to stop is simply amazing.

9.Fill in each blank with the most appropriate word/words. We were expecting a beautiful weather at the beach, but it was so cold and rainy that ––– getting a suntan, I caught a cold.

10.Fill in each blank with the most appropriate word/words. Since the bus companies compete with one another, the drivers have every incentive to drive aggressively and take more passengers than the buses ––– hold.

11.Fill in each blank with the most appropriate word/words. You have to take the full course of your antibiotics ––– you feel better, –––– your illness will simply return.

12.Fill in each blank with the most appropriate word/words. I could not –––– laughing.