Which of the following would be an appropriate null hypothesis?
a. the population proportion is less than 0.65.
b. the sample proportion is no less than 0.65.
c. the population proportion is not less than 0.65.
d. the sample proportion is less than 0.65.

(c) the population proportion is not less than 0.65

Step-by-step explanation:

A null hypothesis must always related  to the population, not the sample, this means you can eliminate B and D option  answers. Since A is strictly less than that means it is an alternative hypothesis because when there is strictly less than then it will be alternative hypothesis.

so the option (c) will be the correct answer