This question considers Horn KBs, such as the following: P(F(x)) ⇒ P(x)

Q(x) ⇒ P(F(x))

P(A)

Q(B)

Let FC be a breadth-first forward-chaining algorithm that repeatedly adds all consequences of currently satisfied rules; let BC be a depth-first left-to-right backward-chaining algorithm that tries clauses in the order given in the KB. Which of the following are true? 

a. FC will infer the literal Q(A). 

b. FC will infer the literal P(B). 

c. If FC has failed to infer a given literal, then it is not entailed by the KB. 

d. BC will return true given the query P(B). 

e. If BC does not return true given a query literal, then it is not entailed by the KB.