Prepositions of Time worksheet with a Venn diagram and fill-in-the-blank exercises.

Task: Fill in the missing prepositions (`in`, `on`, `at`) for the given phrases.

To solve this, we will use the guidelines provided in the Venn diagram on the right side of the image. Here's a summary of the rules:

1. IN:
- Used with:
- Centuries (e.g., the 21st century)
- Decades (e.g., the 1990s)
- Years (e.g., 2012)
- Months (e.g., February)
- Seasons (e.g., spring, summer, autumn, winter)
- General times of the day (e.g., the morning, the afternoon, the evening)

2. ON:
- Used with:
- Days of the week (e.g., Monday, Tuesday)
- Dates (e.g., December 31st, 25th)
- Specific holidays that include "Day" (e.g., Christmas Day, Easter Day)

3. AT:
- Used with:
- Specific times (e.g., 10 o'clock, 7:30)
- Midnight, noon
- Holidays without "Day" (e.g., Christmas, Easter)

Now, let's fill in the missing prepositions for each phrase:

---

#### Left Column:
1. spring → in spring
2. 2012 → in 2012
3. Monday → on Monday
4. Christmas Day → on Christmas Day
5. Easter → at Easter
6. Sundays → on Sundays
7. January → in January
8. the evening → in the evening
9. Tuesday → on Tuesday
10. the morning → in the morning
11. December 31st → on December 31st
12. 10 o'clock → at 10 o'clock
13. September → in September
14. the afternoon → in the afternoon
15. Wednesday → on Wednesday
16. midnight → at midnight
17. Saturday afternoon → on Saturday afternoon
18. noon → at noon
19. Easter Day → on Easter Day
20. Monday → on Monday
21. autumn → in autumn
22. the afternoon → in the afternoon
23. 7 o'clock → at 7 o'clock
24. spring → in spring
25. midnight → at midnight
26. 16th December → on 16th December
27. the evening → in the evening
28. Christmas Day → on Christmas Day
29. noon → at noon
30. 1970 → in 1970
31. winter → in winter
32. Friday morning → on Friday morning
33. Easter → at Easter
34. Saturday → on Saturday

---

#### Right Column:
35. Sundays → on Sundays
36. half an hour → at half an hour
37. the weekend → on the weekend
38. February → in February
39. the evening → in the evening
40. noon → at noon
41. the evenings → in the evenings
42. the moment → at the moment
43. the afternoon → in the afternoon
44. autumn → in autumn
45. 2010 → in 2010
46. Thursday → on Thursday
47. summer → in summer
48. 2011 → in 2011
49. 11 a.m. → at 11 a.m.
50. 16th June → on 16th June

---

Final Answer:

\[
\boxed{
\begin{array}{ll}
1. \text{in spring} & 35. \text{on Sundays} \\
2. \text{in 2012} & 36. \text{at half an hour} \\
3. \text{on Monday} & 37. \text{on the weekend} \\
4. \text{on Christmas Day} & 38. \text{in February} \\
5. \text{at Easter} & 39. \text{in the evening} \\
6. \text{on Sundays} & 40. \text{at noon} \\
7. \text{in January} & 41. \text{in the evenings} \\
8. \text{in the evening} & 42. \text{at the moment} \\
9. \text{on Tuesday} & 43. \text{in the afternoon} \\
10. \text{in the morning} & 44. \text{in autumn} \\
11. \text{on December 31st} & 45. \text{in 2010} \\
12. \text{at 10 o'clock} & 46. \text{on Thursday} \\
13. \text{in September} & 47. \text{in summer} \\
14. \text{in the afternoon} & 48. \text{in 2011} \\
15. \text{on Wednesday} & 49. \text{at 11 a.m.} \\
16. \text{at midnight} & 50. \text{on 16th June} \\
17. \text{on Saturday afternoon} & \\
18. \text{at noon} & \\
19. \text{on Easter Day} & \\
20. \text{on Monday} & \\
21. \text{in autumn} & \\
22. \text{in the afternoon} & \\
23. \text{at 7 o'clock} & \\
24. \text{in spring} & \\
25. \text{at midnight} & \\
26. \text{on 16th December} & \\
27. \text{in the evening} & \\
28. \text{on Christmas Day} & \\
29. \text{at noon} & \\
30. \text{in 1970} & \\
31. \text{in winter} & \\
32. \text{on Friday morning} & \\
33. \text{at Easter} & \\
34. \text{on Saturday} & \\
\end{array}
}
\]