PLS HELP FOR A GRADE THATS IMPORtAANT!!!!!!!!

The heights of all the seniors at Bangor High School follow a normal curve with a mean of 66.4 inches and a standard deviation of 4.3 inches. Which is the correct calculation of the standard deviation of the distribution of sample means based on sample sizes of 16?

a) σx¯¯¯ = 4.366.4√ = .528

b) Cannot be calculated because the sample size is not greater than 30.

c) σx¯¯¯ = 4.316 = .269

d) σx¯¯¯ = 4.316√ = 1.075