(A) The unit "gauss" is used to measure magnetic induction, also known as magnetic flux density, within the CGS system of units.

$$B = {\phi \over A} = {{\max well} \over {c{m^2}}} = gauss\,(CGS)$$

(B) Magnetic intensity (H) is defined as the product of the number of turns per unit length in a coil (n) and the current that it carries (I).

i.e. $$H = nI = {N \over L}I$$

Unit : A/m or Am$^{-1}$

(C) Magnetic flux, $$\phi = BA$$

unit : weber

(D) Magnetic moment (M) : magnetic moment of a current loop, $$M = NIA$$

where, N = number of turns

I = current

A = Area

So, unit = Am$^2$

Hence, option A is correct.