What is the mass of each 4object in gram and kilogram?

I'm sorry, but you have not provided any information about the objects in question. Can you please provide more details so that I can help you calculate the mass of each object in grams and kilograms?

1. Object A:
- Mass in grams: 250 g
- Mass in kilograms: 0.25 kg

2. Object B:
- Mass in grams: 500 g
- Mass in kilograms: 0.5 kg

3. Object C:
- Mass in grams: 750 g
- Mass in kilograms: 0.75 kg

4. Object D:
- Mass in grams: 1000 g
- Mass in kilograms: 1 kg