sell, cell, cel

Sell or sell means to trade for cash or money; to vend--
He decided to sell his old things at a flea market.
She learned to sell real estate and got a new job.

Cell or cell ( rhymes with sell ) means one of the units of a living organism--
Under the microscope, they could see each individual cell.
The hospital did some tests, but they didn't find one cancer cell.
Cell also means one of the locked rooms in a jail or monastery--
He had to share his cell with another convict.

Cel or cel means a transparent image used to make one of the frames of an animated film--
He bought a framed cel from a Disney movie to hang on the wall.
This old cel may be worth some money to a collector.

Now that you know that, you can say--
"He placed an ad to sell an old cel of the dogs in a jail cell from Lady and the Tramp.

Note--the past tense ( yesterday, or some time ago ) form of "sell" is "sold"--
He sold his old things at a flea market last week.
Note # 2--an organism made up of only one cell,  biologically, is called a "single-celled organism"--
We saw a single-celled organism under the microscope.

sole, soul

Sole or sole means the one and only--
The old woman's son was her sole means of support.
The error in his resume was the sole reason they didn't hire him.

Sole also means part of the bottom of a foot or shoe  ( the part that's not the heel )--
The shoe repair shop can fix your sole.
He got a blister on the sole of his foot.

Sole is also a kind of fish--
We had broiled sole for dinner.
Sole in butter is one of my favorites.

Soul or soul ( rhymes with sole ) means the seat of belief--to many people, the spirit of a person--
Many people believed that he sold his soul to the devil.
Some people believe the soul is immortal.

Now that you know that, you can say--
"Religious teaching is the sole reason some people believe they have a soul."

Note--"sold" is the past tense ( yesterday, or some time ago) form of "sell"--
Someone sold him the item on the internet. Then he resold it.
"Soled" is the past tense of "sole", meaning to put new soles on shoes, often called "resoled"--
The shoe repair shop soled my shoes.
I had my shoes resoled at the shoe repair shop.