1) Insert prepositions or post verbal adverbs.
1. In the morning I looked __ the window and was very surprised.
2. Everything was covered _snow! Snowy flakes were falling _the sky!
3. It's not the best time _going out.
4. And I know that some months winter will be over.
5. Summer is a long period _sunshine.
6. Photos will remind us _these exciting days.
7. Britain is _ the ocean, and the water there changes its temperature slower than the ground.
8. I can walk _any umbrella when it's drizzling.
9. The weather the world becomes more and more unusual.

1) In the morning I looked out the window and was very surprised.
Explanation: "Out" is the appropriate preposition to use here because it indicates that I looked from the inside of the house towards the outside through the window.

2) Everything was covered in snow! Snowy flakes were falling from the sky!
Explanation: "In" is the correct preposition to use here because it shows that everything was covered with snow.

3) It's not the best time for going out.
Explanation: "For" is the appropriate preposition to use here because it indicates the reason or purpose for not going out.

4) And I know that some months winter will be over.
Explanation: No preposition or post-verbal adverb is required here. The sentence is grammatically correct as it is.

5) Summer is a long period of sunshine.
Explanation: "Of" is the correct preposition to use here because it indicates what constitutes the long period, which is sunshine.

6) Photos will remind us of these exciting days.
Explanation: "Of" is the appropriate preposition to use here because it shows what the photos will remind us of.

7) Britain is in the ocean, and the water there changes its temperature slower than the ground.
Explanation: "In" is the correct preposition to use here because it indicates the location or position of Britain in relation to the ocean.

8) I can walk without any umbrella when it's drizzling.
Explanation: "Without" is the appropriate post-verbal adverb to use here because it shows the absence of an umbrella.

9) The weather in the world becomes more and more unusual.
Explanation: "In" is the correct preposition to use here because it indicates the weather's condition within the world.