Which of the following is not the unit of length :

The frequency of an electromagnetic wave in free space is 2 MHz. When it passes through a medium of

-- In a p-type semiconductor, the majority charge carriers are

-- The energy of an electron in nth orbit of hydrogen atom is E_n = -13.6/n² eV. The energy required

-- Two magnets of magnetic moments M and 2M are placed in a vibration magnetometer, with like poles

-- For the logic circuit shown below, the truth table is