a) Sulphite process
b) Kraft process
c) Refiner mechanical pulping process
d) Screw pulping process

Answer: c
Explanation: In the 1950s, the refiner mechanical pulping (RMP) process was developed, which produced a stronger pulp and utilized various supplies of wood chips, sawmill residues and sawdust. RMP results in more long fibers than stone groundwood and subsequently stronger paper. However, the energy requirements of RMP are higher and the pulp does not have the opacity of groundwood fibers.