The Null Hypothesis That Two Processes Produce the Same Proportion $p=0$

The null hypothesis that two processes produce the same proportion of defectives can be written

A) $p=0$ .
B) $\frac{x_{1}}{n_{1}}-\frac{x_{2}}{n_{2}}=0$ .
C) $p_{1}-p_{2}=0$ .
D) $\frac{x}{n}=0$ .