English has a lot of different phrases to refer to people in general: the average man (or men) on the street.
“I don’t want every Tom, Dick and Harry walking through my garden.”
In other words,
“I don’t want just anybody who I don’t know walking through my garden.”
In later years, the phrase was modified to recognise that some of the people on the street are female, and Tom, Dick and Sally came into use.
Now for the puzzle.
Tom is looking at Dick, and Dick is looking at Sally.
Tom is married but Sally is unmarried.
Is anybody who is married looking at somebody who is unmarried?
C. It is impossible to know
Here's the answer:
Most people faced with this puzzle, immediately answer C (it is impossible to know) but the correct answer is A (Yes, someone who is married is looking at somebody who is unmarried).
Although we aren't told if Dick is married or unmarried, we know that he must be one or the other.
If Dick is unmarried - Tom who is married is looking at Dick who is unmarried.
If Dick is married - Dick, who is married, is looking at Sally, who is unmarried
So, in either case, the answer is yes.