At Flordyce University any student who wants to participate in a certain archaeological dig is eligible to do so but only if the student has taken at least one archaeology course and has shown an interest in the field  Many students who have shown an interest in archaeology never take even one archaeology course
Ttherefore, many students who want to participate in the dig will be ineligible to do so
For a horse that is well schooled to be ideal for beginning riders that horse must also be surefooted and gentle. Many horses that are surefooted are not gentle. Ttherefore many well-schooled horses are not ideal for beginning riders.