$\begin{array}{1 1} \text{(a) Use of soaps and detergents as cleansing agents} \\ \text{
(b) Molecular structure can be elucidated by surface tension measurements through parachor values} \\ \text{
(c) Surfactants are incorporated in preparations like toothpaste} \\ \text{
(d) All of the mentioned}
\end{array} $
