If the magnetic flux is expressed in $Weber$,then magnetic induction can be expressed in

$A$ coil is placed in a magnetic field such that the plane of the coil is perpendicular to the direction of the magnetic field. The magnetic flux $\phi$ through the coil can be changed by:
$(A)$ Changing the magnitude of the magnetic field $B$.
$(B)$ Changing the area of the coil $A$.
$(C)$ Changing the angle $\theta$ between the magnetic field and the plane of the coil.
$(D)$ Reversing the direction of the magnetic field.

$A$ square of side $x \, m$ lies in the $x-y$ plane in a region where the magnetic field is given by $\vec B = B_0 (3\hat i + 4\hat j + 5\hat k ) \, T$,where $B_0$ is a constant. The magnitude of the magnetic flux passing through the square is:

The magnetic flux linked with a vector area $\overrightarrow{A}$ in a uniform magnetic field $\overrightarrow{B}$ is

When does the magnetic flux become zero?

Which of the following do not exist?