A varactor diode is used primarily for:

a$)$ Voltage regulation

b$)$ Light detection

c$)$ Frequency modulation

d$)$ Power rectification

A "load line" analysis in a transistor circuit is used to determine:

a$)$ The maximum power dissipation

b$)$ The operating point of the transistor

c$)$ The input impedance

d$)$ The cutoff frequency

A "ripple" in the output of a rectifier is caused by:

a$)$ Insufficient filtering

b$)$ Overloading the circuit

c$)$ A short circuit in the diode

d$)$ High input voltage frequency