Three resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel. The total resistance of the combination is

$$R_T = \dfrac{1}{10 \Omega + 15 \Omega + 30 \Omega} = \dfrac{1}{65 \Omega} = 5 \Omega$$

Therefore, the total resistance of the combination is 5 ohms.

Option B is incorrect because 10 ohms is the resistance of one of the resistors, not the total resistance of the combination. Option C is incorrect because 15 ohms is the resistance of another one of the resistors, not the total resistance of the combination. Option D is incorrect because 55 ohms is the sum of the resistances of the three resistors, not the total resistance of the combination.