In each of the following exercises, select the ONE answer that BEST completes the statement or answers the
question. Indicate your solution by circling the letter opposite the correct answer in the subcourse booklet.
Any external disturbances that interrupt or interfere with the normal operation of a receiver are classified
as external noise. Among the types of noise that are classified as external are
galactic, cosmic, and thermal.
solar, cosmic, and terrestrial.
spontaneous emission, and cosmic.
thermal and spontaneous emission.