(1)美洲土著居民很可能在至少一万五千年前迁往加州。
It is likely that Native Americans moved to California at least fifteen thousand years ago.
It is likely that Jacob will dislike the plan.
= Jacob is very likely to dislike the plan.
小结:it is likely/possible/probable that ….
It is possible for sb to do sth
Sb/sth is likely to do sth
Likely 的主语可以是人或物,也可以是形式主语it;而 possible probable 通常只能用it 作形式主语。