Answer:
D. "It must have a small molar mass."
Step-by-step explanation:
In the context of primary standards in chemistry, having a small molar mass is not a typical requirement. Primary standards are substances used in titrations to determine the precise concentration of another substance, often an analyte of unknown concentration. The key characteristics of a primary standard are high purity, non-reactivity with air or water, and a known stoichiometry when reacting. The molar mass of the primary standard is not necessarily small; it should be accurately known to perform the required stoichiometric calculations, but the size of the molar mass is not a primary consideration.