In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

It is said that everyone lives (1)________ selling something. What you can (2)________ from
this statement is that teachers live by selling knowledge, philosophers live by selling wisdom
and priests earn their living by selling spiritual comfort. Though it may be possible to measure
the value of material goods in terms of money, it is extremely difficult to (3)________ the true
value of the services which people perform for us. There are times when we would
(4)________ give everything we possess to save our lives, yet we might grudge paying a
surgeon a high fee for offering us precisely the same service. The (5)________ of society are
such that skills have to be paid for in the same way that goods are paid for at a shop.