Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN) Every day we learn more about the scale and effectiveness of Russian influence operations during the 2016 US election. The implications for our political process are ominous, but the problem runs much deeper. For years hostile foreign governments, terrorist groups, and armies of internet trolls have manipulated public discussion, both in the United States and around the world. We must understand Russia's manipulative attack during last year's presidential elections in a broader context: as a relatively traditional propaganda operation that achieved unprecedented reach because social media companies are either unable or choose not to defend themselves. Every time our society falls victim to an information attack, we blame the attacker, but not their weapons. It's hard to accept that the platforms we use to chat with friends and share baby photos can have such a powerful impact in shaping democracy. Platforms like Google, Facebook, and Twitter have fundamental flaws that must be fixed if we're going to protect ourselves in the future.Jonathon Morgan: For years hostile governments, terrorist groups, and internet trolls have manipulated public discussionSocial media and government have to take steps to prevent this, Morgan says 
 Question:They were manipulating the underlying mechanics of social media, tricking platforms like _, Tumblr, and YouTube into amplifying their message to the widest possible audience.

Twitter