Answer: By the age of 20, Ray has probably lost about 50% of the taste receptors with which he was born.
Explanation: Taste receptors are located on the tongue and in the mouth. They are responsible for detecting the five basic tastes: sweet, sour, salty, bitter, and umami. Taste receptors are constantly being replaced, but the rate of replacement slows down as we age.
By the age of 20, most people have lost about half of their taste receptors. This means that Ray may not be able to taste food as well as he did when he was younger. However, he will still be able to taste food, and he may even be able to develop new tastes as he gets older.
There are a number of factors that can contribute to the loss of taste receptors, including age, smoking, and certain medical conditions. However, even if Ray has lost some of his taste receptors, he can still enjoy food by paying attention to the other senses, such as smell and texture.