The correct answer is (a) Weber.
A Weber (Wb) is the SI unit of magnetic flux. It is named after Wilhelm Weber, a German physicist and mathematician. Magnetic flux is the amount of magnetic field passing through a surface. It is measured by the number of magnetic field lines passing through a surface. The magnetic field lines are imaginary lines that represent the direction and strength of the magnetic field.
The other options are incorrect.
(b) Gauss (G) is the SI unit of magnetic induction. It is named after Carl Friedrich Gauss, a German mathematician and physicist. Magnetic induction is the property of a material that causes a magnetic field to be created around it.
(c) Amp./meter (A/m) is the SI unit of magnetic field strength. It is the magnetic field strength at a point in space.
(d) Oersted (Oe) is the CGS unit of magnetic field strength. It is named after Hans Christian Ãrsted, a Danish physicist and chemist.