What term would you use to describe the tonicity of 0.9% nacl for red blood cells?

It means Red Blood Cell or RBC is isotonic with 0.9% NaCl  solution.

Explanation:

RBC or Red Blood Cell is an important blood cell that play an important role in the transport of Oxygen and Carbon di oxide to and from our body.

          Red Blood Cells are isotonic with 0.9% NaCl solution which means if a red blood cell is kept in a solution containing 0.9% NaCl, it neither swells nor shrinks.That"s why RBC is isotonic with 0.9% NaCl solution.

             This the only reason for using 0.9% NaCl solution as a saline.

correct answer is a. and d.