As three quantities are given, let us apply the formula

M₁H₁D₁=M₂H₂D₂

As per the question,

M₁=18 H₁=16 D₁= 25

M₂=? H₂=9 D₂=8

Apply the values to the formula,

$$\begin{gathered} 18\times 16\times 25=\mathrm{x}\times 9\times 8 \\ \mathrm{x}=\frac{18\times 16\times 25}{9\times 8}=100 \\ \mathrm{x}=100 \mathrm{pumps} \end{gathered}$$

Hence option C is correct.