Make one column out of three

[Mark]

I have three seperate columns, each containing three
different values. For example, column A contains apples,
pears, bananas; column B contains pears, pineapples,
cherries; column C contains pineapples, cherries,
strawberries. I want a quick and easy way to make a
fourth column that contains all the values of A, B, and C
without repeats. So, the fourth column (D) would contain
apples, pears, bananas, pineapples, cherries,
strawberries. I have only been able to do this manually
by copying and pasting the three columns on top of each
other, then sorting and filtering out the repeats.
Wondering about a quicker, more efficient way. Thanks!!