Tugs sometimes shackle a length of chain in the towline in order to __________.

Correct Answer: Option A — put spring in the towline

Chain is significantly heavier than wire or synthetic rope. Inserting a length of chain into the towline creates a catenary effect, which acts as a shock absorber. This 'spring' helps dampen the sudden, violent jerks caused by vessel pitching in heavy seas, protecting the towline and deck equipment from overstress.