What is INCORRECT about reduction?
a.If A can be reduced to B within polynomial time, and B can be reduced to C within polynomial time, then A can be reduced to C within polynomial time.
b.If an NP problem can be reduced to a NP-complete problem, then this problem is also an NP-complete problem.
c.3SAT can be reduced to Vertex Cover problem.
d.If an NP problem can be reduced from a NP-complete problem, then this problem is also an NP-complete problem.