A hollow sphere has a small hole in it. On lowering the sphere in a tank of water, it is observed that water enters into the hollow sphere at a depth of 40 cm below the surface. Surface tension of water is 7×10−2 N/m. The diameter of the hole is approximately:
(A) 0.21 mm
(B) 0.14 mm
(C) 0.07 mm
(D) 0.7 mm