which of the following is a well-defined set?
a.A set of beautiful sceneries
b.A set of good basketball players
c.A set of Philippines presidents
d.A set of successful leaders

list all the letters in the word "school"
a.{s,c,h,o,o,l}
b.{s,c,h,o,l}
c.{s,h,o,o,l}
d.s,c,o,l}

Given the set of letters in the word "mathematics" , what is the cardinality of the given set?
a.11
b.8
c.6
d.4
with example pls...​