$\text{Dane:}$  

$\text{m}=1\text{kg}$  

$\Delta \text{T}={10}^{\circ }\text{C}$  

${\text{c}}_{\text{w}}=4200\frac{\text{J}}{\text{kg}{\cdot }^{\circ }\text{C}}$  

$\text{Szukane:}$  

$\text{Q}=\text{?}$  

Obliczamy ilość ciepła: 

$\text{Q}={\text{c}}_{\text{w}}\cdot \text{m}\cdot \Delta \text{T}=4200\frac{\text{J}}{\sout{\text{kg}{\cdot }^{\circ }\text{C}}}\cdot 1\sout{\text{kg}}\cdot 10\sout{{}^{\circ }\text{C}}$  

$\text{Q}=42000\text{J}=42\text{kJ}$  

Odpowiedź: D. 42 kJ