Answer:
One.
Step-by-step explanation:
SDS (sodium dodecyl sulfate) PAGE ( Polyacrylamide gel electrophoresis) is the technique of the separation of the molecules on the basis of their molecular weight.
The beta-mercaptoethanol reduces and break the disulfide bonds present in the protein. When the protein X with the beta-mercaptoethanol is allowed to run on the gel, only one band will visible all the subunits have equal weight and will present at the same location on the gel.
Thus, the answer is one.