instruction:
Given a scientific question, generate a correct answer to it.
question:
On the ventral side of the embryonic disc, opposite the amnion, cells in the lower layer of the embryonic disk (the hypoblast) extend into the blastocyst cavity and form this?
answer:
yolk sac

question:
Do particles collide more in two reactants when they are both in fluid forms or solid forms?
answer:
fluid

question:
What is added to alcohol and used as an antiseptic?
answer:
iodine