This is difficult, as it seems to be asking for word selections from a word bank which you have not posted. So although this may not be the correct answer, maybe you will get the right idea or find it to be a simile of the correct answer.
"We LABOR many hours a day, working hard at our desks with keyboards and screens."
Opportunity cost is when you have a choice between a number of things. The thing/things you didn't choose are the opportunity cost, if that makes any sense.
