Answer:
Always when we have a statement like:
"all of {some group} have {a given property}"
A counterexample of this is:
"There exists at least one element of the given group that does not meet the property"
Then we have the statement"
All basketball players are most than 6 ft tall
The counterexample would be:
There exist one basketball player that measures 6ft
or
There exist one basketball player that measures less than 6ft
