单选题 ______ that the formation of the sun, the planets, and other stars began with the condensation of an interstellar gas cloud.

【正确答案】 A

【答案解析】[解析] 本题测试形式主语。这是一个主语从句后置的句型。因为主语从句过长，故用一个形式主语it代替。It is believed that意为“大家都相信”，相同句式还有it is well known that，意为“众所周知”。