Final answer:
Milliequivalents accurately measure the reactivity of electrolyte solutions because they consider the concentration of ions and their charges; therefore, the statement is true.
Step-by-step explanation:
Milliequivalents are indeed an accurate measure for the physiological combining power, or reactivity, of a particular electrolyte solution. This is because a milliequivalent (mEq) takes into account both the amount of substance (in millimoles) and the charge on the ions present. Specifically, for ions with a single charge, one mEq is equal to one millimole, while for divalent ions like calcium, one mEq equals 0.5 millimoles.
Considering this, the statement in the student's question is true. Electrolyte concentrations in the body are typically expressed in mEq because body fluids are usually within the range of 280 to 300 milliosmoles (mOsm), and precise osmotic pressure balance is crucial for biological functions.