From the list provided at the right, select the word or phrase that is defined or indicated$\mathrm{.}1.$ aRevenue and expense accounts$\mathrm{.}2.$ An optional step in the accounting cycle$\mathrm{.}3.$ A revenue collected, but not recognized$\mathrm{.}4.$ A revenue recognized, but not collected$\mathrm{.}5.$ Asset, liability, and equity accounts$\mathrm{.}6.$ An expense paid, but not incurred$\mathrm{.}7.$ An expense incurred, but not paid.