Which of the following sentences contains formal contains formal language, rather than…

Which of the following sentences contains formal contains formal language, rather than informal language?
a) When traveling alone, be on the lookout for pick-pockets
b) I didn’t want to tell on my friends, but the teacher gave me no choice.
c) If you can’t take the heat, get out of the kitchen.sd
d) The blue – footed booby is a magnificient specimen.