One Reason That Phone Numbers in the United States Are

Multiple Choice

One reason that phone numbers in the United States are seven digits long is that __________.

A) most people can transfer seven digits into long-term memory instantly, bypassing short-term memory
B) this is the maximum number of items that can be held in short-term memory at a given moment
C) sensory memory for numbers is very keen and can handle such a large quantity of digits
D) when polled, early phone customers requested this many digits in their phone numbers