Question

support structures
use the information below to answer the question.
need
a support structure is not needed with powder - based printing, such as sls sand or polymer. however, with metal printing, a support will be needed to control the warpage and to dissipate heat into the build plate.
most slicing programs for fused filament fabrication (fff) will have an option to automatically add support. support can also be added manually to any spot that needs more.
with sla, the considerations differ depending on whether the printer is a bottom - up or top - down machine. there are also choices as to how the support material is created.
removal
a support structure can be removed by sanding, vapor smoothing (with abs filament), or using a grinder for direct metal laser sintering (dmls).
fff and material jetting can use dissolvable support structures as well. an fff machine will need two spools - one for the build material and one for the support material. with material jetting, there will be two bins. with fff, there are different ways the filament can be dissolved, depending on the type of filament. one uses a chemical process; the other uses water, which is probably safer.
which two printing processes can use dissolvable support structures?
vat polymerization (vat) and selective laser sintering (sls)
direct metal laser sintering (dmls) and binder jetting (bj)
fused filament fabrication (fff) and material jetting (mj)
stereolithography (sla) and direct light processing (dlp)

Explanation:

The text mentions that Fused Filament Fabrication (FFF) and Material Jetting (MJ) can use dissolvable support structures. FFF has options for support addition and different ways to dissolve the filament (chemical or water). Material Jetting has two bins, which is relevant to the use of dissolvable support structures.

Answer:

Fused Filament Fabrication (FFF) and Material Jetting (MJ)