On heating water, bubbles being formed at the bottom of the vessel detatch and rise . Take the bubbles to be spheres of radius R and making a circular contact of radius r with the bottom of the vessel . If r << R , and the surface tension of water is T , value of r just before bubbles detatch is : (density of water is $\;\rho_{w}$)

$(a)\;R^{2} \; \sqrt{\large\frac{\rho_{w} g}{3T}}\qquad(b)\;R^{2} \; \sqrt{\large\frac{\rho_{w} g}{6T}}\qquad(c)\;R^{2} \; \sqrt{\large\frac{\rho_{w} g}{T}}\qquad(d)\;R^{2} \; \sqrt{\large\frac{ 3\rho_{w} g}{T}}$