Explanation:

- To find the mass of the material, we use the formula: \( Q = mc\Delta T \), where \( Q \) is the heat energy, \( m \) is the mass, \( c \) is the specific heat capacity, and \( \Delta T \) is the change in temperature.

- Given: Specific heat capacity \( c = 400 \) J/kg°C, \( Q = 20 \) kJ (or 20000 J), and change in temperature \( \Delta T = 25°C - 15°C = 10°C \).

- Rearrange the formula to find mass: \( m = \frac{Q}{c\Delta T} = \frac{20000}{400 \times 10} \).

- Calculating gives \( m = \frac{20000}{4000} = 5 \, \text{kg} \).

- Option:4- 5 kg is correct.