TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Blood is made up of red blood cells, white blood cells, platelets, and plasma.

SOLUTION: Blood is made up of red blood cells, white blood cells, platelets, and what else?

PROBLEM: Human facial expressions can communicate emotions.

SOLUTION: What can human facial expressions communicate?

PROBLEM: Complement proteins proteins bind to the surfaces of microorganisms and are particularly attracted to pathogens that are already tagged by the adaptive immune system.

SOLUTION:
Which proteins bind to the surfaces of microorganisms and are particularly attracted to pathogens that are already tagged by the adaptive immune system?