Final answer:
Mustapha Mond uses the Biblical phrase 'Suffer the children' when children begin playing around him in Aldous Huxley's 'Brave New World'.
Step-by-step explanation:
The Biblical phrase that Mustapha Mond uses when children begin playing around him is b. Suffer the children. This phrase is reflective of his character's complex relationship with the principles of the society he oversees in Aldous Huxley's Brave New World. While society largely rejects traditional religion and its values, Mond uses this Biblical reference, indicating an awareness and perhaps a veiled endorsement of some of its moral stances on the innocence and significance of children.