The correct answer is C) kink in the line. Improperly coiling manila line can lead to the formation of kinks, which are tight bends or loops in the line. These kinks can reduce the overall strength and integrity of the line, making it more prone to breaking or failing under strain. Kinks in the line can also make it difficult to smoothly deploy or retrieve the line, which is crucial for safe and effective use on a vessel. The other answer choices are not directly related to the consequences of improperly coiling manila line. The number of fishhooks (A) is not a relevant factor, and a 50% loss of efficiency (B) or an increase in deterioration (D) are not direct outcomes of improper coiling, but rather general effects of line wear and damage over time.