Which of the relations below is a function?

{(red, sign) (yellow, sign) (red, light) (green, light)}

{(blue, bird) (red, car) (yellow, bus) (yellow, taxi)}

{(red, apple) (purple, grape) (yellow, banana) (green, pear)}

Ifound this on google “a skewed (non-symmetric) distribution is a distribution in which there is no such mirror-imaging. a "skewed right" distribution is one in which the tail is on the right side. a "skewed left" distribution is one in which the tail is on the left side. the above histogram is for a distribution that is skewed right.” i hope this you for what your looking for