Answer:
A: undercoverage bias
Step-by-step explanation:
Undercoverage bias occurs in a study or sampling when some elements of the sample population are not represented or inadequately represented.
In this case study, random sampling using phone book will not adequately represent the true size of the population since 4% have no phone, and 15% have unlisted home numbers, while only 10% have only cell phones. This sampling suffers from undercoverage bias