The Candy Company That Makes M&M's Claims That 10% of the M&M's

The candy company that makes M&M's claims that 10% of the M&M's it produces is green.Suppose that the candies are packaged at random in large bags of 200 M&M's.When we randomly pick a bag of M&M's,we may assume that this represents a simple random sample of size n = 200.Suppose we wish to test H₀: p = 0.10 versus H_a: p $\neq$ 0.10.Under the null hypothesis,what is the value of the standard error of ,the sample proportion of green M&M's in a bag of 200?

A) 0.0015
B) 0.021
C) 0.09
D) 18