The correct answer is C) The latch of a safety hook prevents the sling ring from coming out of the hook if the strain is abruptly eased. The purpose of the latch on a safety hook is to prevent the sling ring from accidentally coming out of the hook if the load is suddenly released or the tension is quickly reduced. This helps maintain the integrity of the lifting system and prevent accidents. The latch does not increase the overall strength of the hook itself (option B is incorrect) nor does it specifically prevent the sling ring from coming out under constant strain (option A is incorrect). Option D is also incorrect as the latch's primary function is not all of the listed purposes.