It seems reasonable_______that peopled behaviour is influenced by what they see on TV.
在动词不定式结构中，有该句型“It +be/seems/appear+adj+to do sth”,表示“做某事是/看起来是……的”故答案C正确。
翻译：人们的行为会受到他们在电视所看到东西的影响，这件事看起来很合理。