Select the true statements about SDS‑PAGE, a method of separating proteins. Assume that SDS‑PAGE is performed under reducing conditions.

a. Proteins are separated in a polyacrylamide gel matrix.
b. Protein‑SDS complexes have similar mass to charge ratios; therefore, separation is by size.
c. Proteins are visualized using a dye that binds to the gel matrix, but not to proteins.
d. Smaller proteins migrate faster through the polyacrylamide gel.
e. Sodium dodecyl sulfate binds proteins, resulting in protein‑SDS complexes that are similar in size.
f. Protein‑SDS complexes migrate toward the negative electrode.