The Republican-controlled House of Representatives voted in favor of the Keystone XL Pipeline on January 9, 2015. Representatives voted 266 to 153 to allow Canadian oil producers to build the TransCanada Keystone XL Pipeline through the Midwest from Montana to the Gulf of Mexico. Environmentalists opposed the pipeline as having limited economic value in producing new jobs for American citizens.

Which of these represents the who of this paragraph?

Representatives
Canadian oil producers
Environmentalists
American citizens