Here are the completed sentences:
- He is in the garden.
- They are at the school.
- I am a good student.
- Marie is a police officer.
- You are 10 years old.
- The dog is in the box.
- We are in the car.
- She is my sister.
To determine which form of the verb 'to be' to use (am, is or are), we look at the subject of the sentence:
- For 'he', 'she' or 'it', we use 'is'
- e.g. He is in the garden. She is my sister.
- For 'I' or 'you', we use 'am' or 'are'
- e.g. I am a good student. You are 10 years old.
- For subjects in plural form (they, we), we use 'are'
- e.g. They are at the school. We are in the car.
Hope this helps! Let me know if you have any other questions.