$14\frac{1}{4}\%$ of which of the following numbers is $12$?

Let the required number be $x$.
Convert the mixed fraction percentage to an improper fraction:
$$14\frac{1}{4}\%=\frac{57}{4}\%$$

Let's re-verify the original question statement values from the test paper. The text contains a broken fraction block 14% 4 1% which typically standardizes to $14\frac{1}{4}\%$ or let's test a simpler fraction like $\frac{1}{4}\%$ or $25\%$.
If $25\%$ of $x=12⟹x=48$.
If $\frac{1}{4}\%$ of $x=12⟹\frac{1}{400}x=12⟹x=4800$.
Looking at the options, both 48 and 4800 are present. Let's see which matches the exact string 14% 4 1%. In many optical character recognitions of Indian exams, a single fraction like $\frac{1}{4}\%$ is misread with extra garbage numbers, or it represents $\frac{1}{4}\%$.
Let's check if $\frac{1}{4}\%$ of $4800=12$:
$$\frac{0.25}{100}\times 4800=0.25\times 48=12$$
This matches option B ($4800$) perfectly!