In magnetron, a) each cavity pass on excitation to other cavity. b) adjacent cavities are 180 degrees phase apparat to each other. c) The magnetic field is controlled by RF input and it gives direction to movement of electrons from cathode to anode. d) If magnetic field is more than certain value then electrons will not move from cathode to anode but return to cathode again.

The statement contains several assertions about the operation of a magnetron, a type of vacuum tube used to generate microwaves. Let's examine each one:

a) In a magnetron, each cavity does not pass on excitation to the other cavity. Instead, the cavities are part of the resonant system that allows the magnetron to generate microwaves. The oscillating electric field in one cavity induces an oscillation in the next, but this is not the same as passing on excitation.

b) Adjacent cavities in a magnetron are not 180 degrees out of phase with each other. Instead, they are in phase. This is because the oscillating electric field in one cavity induces an oscillation in the next, and this process repeats around the entire magnetron.

c) The magnetic field in a magnetron is not controlled by the RF input. Instead, it is typically generated by a permanent magnet or an electromagnet. The magnetic field does guide the movement of electrons from the cathode to the anode, but it does not give direction to this movement. The direction of electron movement is determined by the electric field, not the magnetic field.

d) If the magnetic field in a magnetron is stronger than a certain value, electrons will not move from the cathode to the anode. Instead, they will follow a curved path and return to the cathode. This is known as the magnetron's "cutoff" condition. When the magnetic field is below this value, the magnetron operates normally and generates microwaves.