National security is the prevailing theme of lawmakers’ questions.

Lawmakers of the House Energy and Commerce Committee pursued accountability and transparency from TikTok’s chief executive, Shou Chew, in a five-hour hearing on Thursday, accusing the company of keeping ties to the Chinese government and having harmful effects on children and teenagers.

TikTok, which has 150 million users in the United States, has come to represent the growing divide between the U.S. and China over tech leadership and national security — its parent company, ByteDance, is Chinese. The app has become a battleground in a technological cold war between the two countries, with U.S. threats of a TikTok ban recalling how China has long blocked many American platforms.

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