If average of 20 observations $x_{1}, x_{2}, ...., x_{20}$ is y, then the average of $x_{1} - 101, x_{2} - 101, x_{3} - 101, ...., x_{20} - 101$ is:
[A] $101y$
[B] $20y$
[C] $y - 101$
[D] $y- 20$