How should we write the alternative hypothesis to determine if the opinions of American adults have changed over the last decade?

a. LaTeX: Ha: p_{1}-p_{2} \ne 0 H a : p 1 − p 2 ≠ 0
b. LaTeX: Ha: \hat{p}_{1}-\hat{p}_{2} \ne 0 H a : p ^ 1 − p ^ 2 ≠ 0
c. LaTeX: Ha: p_{1}-p_{2} > 0 H a : p 1 − p 2 > 0
d. LaTeX: Ha: \hat{p}_{1}-\hat{p}_{2} >0