The correct answer is the following.
Missionaries were affected by the Boxing Rebellion because they suffered aggressions and many were killed.
The Boxer Rebellion was a movement in China organized by the Society of Righteous and Harmonious Fists. The rebellion was an anti-Christian protest movement that turned violent in its actions. It lasted from 1889 until 1891. The group was against imperialism and the presence of Christian evangelists in China. People committed aggressions against Christian evangelist and many evangelists were killed.
