6. [2 pts] Which one of the following is correct about the process of pilgering: (a) Its primary purpose is to enlarge the diameter of a hollow tube; (b) The resulting tube often has a greater thickness; (c) It is typically done on a heated drawing machine; (d) The mother tube, as a beginning workpiece, has to have perfect straightness for the pilgering to work well; (e) It is meant to be the costly replacement of the rotary tube piercing process, for a higher throughput; (f) The finished tube dimensions are determined by the mandrel and a pair of ring dies. 5. [2 pts] Which one of the following is incorrect about the P/M sintering process using green compact as a starting material -- (a) It increases the degree of densification of green compacts; (b) Heat and pressure are applied simultaneously; (c) It reduces surface contact area between particles through atomic transport; (d) It is often done at a temperature below melting point; (e) It eliminates the pores between particles; (f) It improves the mechanical strength of the part.