Correct Answer - Option 4 : Gilbert
Gilbert (Gb) is a unit in the category of Magnetomotive force. It is also known as gilberts. This unit is commonly used in the cgs unit system. Gilbert (Gb) has a dimension of I where I is electric current. It can be converted to the corresponding standard SI unit A by multiplying its value by a factor of 0.79577.
The Advisory Committee on Nomenclature of the IEC adopted the name gilbert for the cgs unit of magnetomotive force in 1930, at its meetings in Scandinavia¹. It is named for William Gilbert (1544 – 1603).