Which of the Following Statements Reflects the Fluid Quality of Income

Which of the following statements reflects the fluid quality of income?

A) It is very difficult to quantify.
B) It flows in the form of paychecks and flows out as bills are paid and daily expenses are met.
C) U.S.household incomes have largely stagnated over the past decades.
D) It is illiquid, meaning that it is logistically difficult to transform into cash.