Cloudy nights are warmer than clear ones because

Question

$\begin{array}{1 1} (a)\; \text{clouds absorb heat in the day and supply it in the night } \\ (b)\; \text{clouds reflect back heat radiations to the earth} \\ (c)\; \text{heat of the earth's atmosphere increases in the presence of clouds} \\ (d)\; \text{clouds absorb cold radiations and reflect back hot radiations} \end{array}$