To understand the phrase "make common cause with," we need to identify situations where two or more parties come together with a shared goal or mission. This involves setting aside differences to unite for a particular purpose, usually involving cooperation or collaboration against a common issue.
Given the options:
- I need to figure out how to fit the piano and the bookshelf in this room.
- Environment protesters have parted ways with the local people to stop the establishment of the factory.
- The police were acting on a tip from an informer and caught the gang redhanded.
- The crowd backed away when the man pulled out a knife and most of them cried for help.
We need to find the scenario in which entities unite for a mutual cause. Option 2 is the correct choice: "Environment protesters have parted ways with the local people to stop the establishment of the factory." Here, the phrase "to stop the establishment of the factory" implies a shared mission between the protesters and local people collaborating towards a common goal, despite having previously parted ways.