Final answer:
The prescription is for Tobramycin/Dexamethasone eye drops 1 gtt OS q6h. The correct expression of the dosage using the official symbol and a half percent is option a: Tobramycin/Dexamethasone eye drops 1 gtt OS 0.5%.
Step-by-step explanation:
The prescription states Tobramycin/Dexamethasone eye drops 1 gtt OS q6h. The medication is Tobramycin/Dexamethasone eye drops, and the dosage is 1 gtt (one drop) to be administered in the left eye (os) every 6 hours (q6h).
The prescription also mentions the concentration of the eye drops. In option a, 0.5%, the concentration is half a percent. Option b, 1/2%, also represents half a percent. Option c, 0.05%, represents 0.05 percent. Option d, 50%, represents 50 percent.
Therefore, the correct expression of the dosage using the official symbol and a half percent is option a: Tobramycin/Dexamethasone eye drops 1 gtt OS 0.5%.