It is ( ) that.那个括号填believe的什么形式啊

believed
有不明白的地方再问哟,祝你学习进步,更上一层楼! (*^__^*)为什么It is believed 是固定搭配人们普遍认为eg：It is believed that almost all sudden deaths are caused by damage to the heart.人们相信大多数的突发死亡都是由心脏受损引起的