Answer:
The most severe constraint that anyone faces is time, the day has 24 hours, a week has 7 days and the year has 365 days. No matter how big or small a company is, time is the same for all. E.g. a factory has to build 10,000 units of good X for next week, they must do it before the due date. If the factory is shut down for any reason at all, e.g. lights go out, they will have to work overtime.
Two of the other constraints are basically related to capital: equipment and facilities. No matter how rich a person is or how big a company is, they have a certain amount of money, they cannot own it all. Only governments own machines that print money, and even they face strict regulations regarding how much money they can print. You need money to buy more equipment and build larger facilities, or if you do not have enough money, you will have to work overtime or eventually not be able to produce the output that you wanted. A facility has a certain level of maximum production, the same for a machine or equipment, and you cannot make it work over that level. E.g. a machine produces 10 units per hour, so it will not be able to produce 100 units per hour, nor 20 nor 40, not even 11.
Labor constraints refer to the total amount of labor supply available. E.g. all you need to do to understand the shortage of certain qualified labor is look at the amount of job vacancies in the high tech, computer and software industries. There are hundreds of thousands of vacant jobs around the world which cannot be filled simply because there are not enough qualified people. That is also the reason why careers in these industries are paid higher than average wages.
