$277.$ Frother is added in the froth floatation cell used in ore beneficiation to stabilise the air bubbles $($i$.$e$.,$ froth$),$ which will hold the ore particles, but it does not affect the floatability of minerals. Which of the following is not used as a frother?

Cresylic acid

Xanthaies

Pine oil

All $\text{'}$a$\text{'}\text{'}$b$\text{'}$ & $\text{'}$c$\text{'}$