The correct option is
B To restrain
Option C is the correct answer because the phrase 'hold in' means to hold in restraint.
Options A, B, D and E are incorrect because 'to refrain' means to top oneself from doing something, 'to abstain' means to choose not to do or have something, 'to maintain' means to continue to have; to keep in existence and 'to entertain' means to provide (someone) with amusement or enjoyment.