(a) The requirement is to identify the method to prevent
data eavesdropping. Answer (a) is correct because data
encryption prevents eavesdropping by using codes to ensure that
data transmissions are protected from unauthorized tampering or
electronic eavesdropping. Answer (b) is incorrect because dial
back systems ensure that data are received from a valid source.
Answer (c) is incorrect because message acknowledgment procedures
help ensure that data were received by the intended
party. Answer (d) is incorrect because password codes are designed
to prevent unauthorized access to terminals or systems.