One teaspoon full is equal to:

Correct option is C

In medical measurement, 1 teaspoon is standardized to 5 milliliters, especially for pediatric medication dosing. Explanation of options:
· (a) ✘ 15 ml is a tablespoon.
· (b) ✘ No standard measure matches this.
· (c) ✔ Correct; 1 tsp = 5 ml.
· (d) ✘ 20 ml equals 4 teaspoons.