Spring constant has units N·m^-1, which is the same as surface tension units (N·m^-1), so option C is correct per the answer key.

Young's Modulus is stress divided by strain, which is the gradient (slope) of the stress–strain graph.

When iron is in the boat it displaces water equal to its weight; when thrown in, it displaces water equal to its volume (less), so the level falls.

Steradian is the unit of solid angle, not plane angle; degree, radian and gradian are plane-angle units.

Steradian is the SI unit for solid angle; radian is for plane angle and candela is luminous intensity.

The block header indicates option B as the answer (Stokes' law form F = 6π η r v) per the OCR answer key.

In C.G.S., stress has units of force per unit area, i.e., dyne/cm^2 (dyne per square cm).

m = W/g, so m = 196 N / 9.8 m/s² = 20 kg.

Current density has both magnitude and direction (direction of charge flow per unit area), so it is a vector; electric current is treated as a scalar.

Coulomb is a derived unit (unit of electric charge); kilogram, ampere and mole are SI base units.