In the movie industry, either "stunt double" or "body double" depending on exactly what they're doing.
Doppelganger
a persons shoe sise is....
A bed that can accommodate two persons.
The answer to country persons (us) is hayseeds
"French".
Bias
The measure of the amount of alcohol in a persons blood is called the blood alcohol concentration (BAC).
The measure of the amount of alcohol in a persons blood is called the blood alcohol concentration (BAC).
lit o' bit mate
It could be called a gala.
They are called trigonometricians.
ka
Their surname.