According to the question,

Let us assume

time taken by B = x

then time taken by A = 2x

and time taken by C =3x

$=\frac{1}{x}+\frac{1}{2x}+\frac{1}{3x}=\frac{1}{12}$

⇒ $1+\frac{1}{2}+\frac{1}{3}=\frac{x}{12}$

$$\begin{gathered} \Rightarrow \frac{6+3+2}{6}=\frac{x}{12} \\ \Rightarrow 11=\frac{x}{2} \end{gathered}$$

∴   x=22

∴ Required no. of days= 2x= 2×22= 44 days

Hence option D is the correct .