Anchor: Still, every now and then, a professor would have four genuine A students and only three A's to give out.
Entailed: Even so, sometimes a professor could have four students who deserved A's but could only give A's to three of them.
Contradiction: Professors always have four A's to hand out to four A students. 
Contradiction: A man is standing on the ground.
Contradiction: The requirement for the final rule will help the organ sharing system to be most effective.
Contradiction: Yes that one is the set apart mulching mower we talked about.
Contradiction: People walking on a busy city street.