1．However, it_is_likely_that Native Americans were living in California at least fifteen thousand years ago.
然而，美洲土著人有可能在至少15 000年前就在加州生活着。
本句式中 it为形式主语，真正的主语为 that从句。
It is likely that... ……是可能的。此句型可转化为：Sb./Sth. be likely to do... 某人/物可能干某事。
①She‘s very likely to ring me tonight.
