Given that,

Let the total number of apples in the crate = A

Then, number of bruised apples= $\frac{a}{40}$

Number of unsaleable apple

Since, 4 bruised apple containing 3 unsaleable apple

∴ 1 bruise apple will contain $\frac{3}{4}$ unsaleable apple

Hence, $\frac{a}{40}$ bruise apple will contain $\frac{3}{4}\times \frac{a}{40}$ unsaleable apple

$$\begin{gathered} = \frac{3}{4}\times \frac{a}{40}=\frac{3a}{160} \\ From the question, \\ = \frac{3a}{160}=9 \\ a=9\times \frac{160}{3} \\ a=3\times 160=480 \end{gathered}$$

Hence, Option C is correct.