- A vegetable is a kind of plant
- An onion is a kind of vegetable
- Therefore, an onion is a kind of plant

- A plant cell is box-like in shape
- A plant is made of plant cells
- So, a plant is made of box-like plant cells

- An onion is a kind of plant
- A plant is made of box-like plant cells
- So, an onion is made of box-like onion cells

- An onion is made of box-like onion cells
- A lots of box-like objects are seen under a microscope on a slice of onion
- So, the objects seen under the microscope are onion cells

So, the objects seen under the microscope are onion cells
When a thin slice from an onion is viewed through a microscope, lots of little box-like shapes are seen. These shapes are most likely
- A plant cell is box-like in shape 
- A plant is made of plant cells 
- A vegetable is a kind of plant 
- An onion is a kind of vegetable 
- A lots of box-like objects are seen under a microscope on a slice of onion