Answer
a) Differential and selective
Work Step by Step
It is differential because it allows the identification of lactose-fermenting gram-positive bacteria by means of the pH indicator, which turns fermenting colonies red and non-fermenting colonies pink.
MacConkey is a complex medium (it contains peptone from different origins) therefore it cannot be classified as a defined medium (as option c indicates).
Options b and d are incomplete.
Option e is incorrect, since regulatory is not a media type.
