1. Capillary rise formula

For a liquid rising in a capillary tube of radius $r$, the height of rise is

$h = \frac{2T\cos\theta}{\rho g r}$

where:

• $T$ = surface tension
• $\theta$ = angle of contact
• $\rho$ = density of liquid
• $g$ = acceleration due to gravity

So,

$h \propto \frac{1}{r}$

2. Mass of liquid risen in the tube

The mass of water in the tube is

$m = \rho \times \text{volume} = \rho \pi r^2 h$

Substitute $h \propto \frac{1}{r}$:

$m \propto r^2 \cdot \frac{1}{r} = r$

Thus, the mass of water risen is directly proportional to the radius of the tube:

$m \propto r$

3. Compare tubes of radius $r$ and $2r$

If for radius $r$, the risen mass is $M$, then for radius $2r$,

$m' \propto 2r$

Hence,

$m' = 2M$

4. Option check

• A: $M$ ❌
• B: $4M$ ❌
• C: $M/2$ ❌
• D: $2M$ ✅

Therefore, the correct answer is:

$\boxed{2M}$