Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage

Choose the word or phrase among A, B, C or D that best fits the blank space in the following
of the famous San Fermin festival - a practice
passage
The Running of the Bulls is a (27)_
that involves running in front of a small group of bulls (typically a dozen) that have been let
loose on a course of a town's streets. A first firework is set off at 8 a.m. to alert the runners
that the corral gate is (28)
A second firework signals that all six bulls have
(29)
released. The third and fourth fireworks are signals that all of the herd has
entered the bullring, marking the end of the event. Every year between 200
(30)
injured during the run (31)_
are not serious. So you think you support it?
and 300 people
are due to falls and
most injuries