Before revision: Political Opportunities: uf the existing political system is vulnerable to a challenge, it creates an opportunity for others, like the movement members, to issue such a challenge and try to use this opportune time to push through a social change.
After revision: Political Opportunities: if the existing political system is vulnerable to a challenge, it creates an opportunity for others, like the movement members, to issue such a challenge and try to use this opportune time to push through a social change.