At the same temperature, a $0.05\mathrm{M}$ solution of $\mathrm{NaCl}$ (assume complete dissociation) is isotonic with

Isotonic solutions have equal total particle concentration at the same temperature. $0.05\mathrm{M}$ $\mathrm{NaCl}$ gives $2\times 0.05=0.10$ M of particles. $0.10\mathrm{M}$ glucose does not dissociate and also gives 0.10 M. $\mathrm{CaCl}{}_2$ at 0.05 M would give 0.15 M.