If $\bar{x}$ is the means of n observations $x_1,x_2,.....x_n$ then the mean of the observations $x_1 +a, x_2 +a, ....... x_n +a$ is _________

Question

$(A) \; n\bar {x} +a \\(B)\; \bar {x}+a \\(C)\; n \bar {x} -a \\(D)\;\bar {x} -a$