The slew rate of an operational amplifier is defined as the rate at which the output voltage changes in response to a change in the input voltage. It is typically represented as the change in output voltage per unit time, expressed in volts per microsecond (V/µs), indicating how fast the output can change.
Therefore, the correct representation of the slew rate is:
(c) 1V/µs.
This means the output voltage can change by 1 volt in one microsecond.