If the following reactions are elementary, which reactor configuration would improve the selectivity to product D? (D = desired) Explain your answer!

2A + B D

A + 2B U

(a) Feed A through a series of CSTRs, add a little B to each

(b) Load B into a semibatch reactor, add A as a side-stream

(c) Feed B into a PFR, inject side streams with A

(d) Feed A and B into a PFR

(e) Feed A and B into a CSTR