好的，以下是 50 个有关句子做主语的句子：

1. The cat is playing with a ball.

2. The dog is running in the park.

3. The sun is shining brightly today.

4. The car is parked in the garage.

5. The boy is playing video games all day.

6. The girl is reading a book in the library.

7. The apple is rolling down the hill.

8. The dog is barking loudly at the mailman.

9. The baby is crying out for a diaper change.

10. The boy is ice skating on the lake.

11. The girl is dancing in the rain.

12. The tree is bleeding green leaves in the wind.

13. The man is sitting on a bench sipping a beer.

14. The woman is shopping for groceries at the market.

15. The car is speeding down the highway.

16. The dog is jumping up to catch a Frisbee.

17. The boy is building a sandcastle on the beach.

18. The girl is composing a poem on her desktop.

19. The sun is setting over the horizon.

20. The dog is chasing a small toy across the yard.

21. The girl is playing with her new toy doll.

22. The boy is practicing his piano in the music room.

23. The apple is falling from the tree onto the ground.

24. The dog is growling with excitement in the living room.

25. The woman is making a pot of tea in the kitchen.

26. The boy is exploring the streets of his neighborhood.

27. The girl is painting a picture on the back of a book.

28. The dog is snarling in the front yard, warning the mailman.

29. The sun is peaking behind a cloud cover over the city.

30. The boy is having a picnic in the park with his friends.

31. The girl is reading a book in the public library.

32. The dog is barking loudly at the door, waiting for someone to arrive.

33. The man is walking his dog in the park at night.

34. The woman is making a salad in the kitchen.

35. The boy is building a treehouse in the backyard.

36. The girl is practicing her singing voice in the bathroom.

37. The dog is jumping up onto the bed, begging for a treat.

38. The sun is shining down on the beach during the summer.

39. The boy is rollerblading on the sidewalk in the city.

40. The girl is making a cake in the kitchen for her friend's birthday party.

41. The dog is barking at the mailman, wanting to receive a letter.

42. The man is sitting on a bench, reading a book and waiting for his wife to arrive.

43. The woman is doing the laundry in the bedroom.

44. The boy is playing a video game in his bedroom.

45. The girl is walking her dog in the park at midnight.

46. The dog is growling and jumping up, trying to chase a small toy away.

47. The sun is setting in the horizon, casting a warm orange glow over the landscape.

48. The boy is practicing his martial arts in the gym.

49. The girl is writing a story in the notebook.

50. The dog is waiting patiently by the door, waiting for the mailman to arrive.