想请英语语法老师解释下句型中的语法现象.
问题描述：
想请英语语法老师解释下句型中的语法现象.
1.Geneticists explain that since closely related persons are more likely to harbor identical genetic mutations,their children have a greater chance of being born with defects
请解释下其实中的are more likely to harbor的语法现象.
2.Although the risk is still significant,it is lower than previously thought.
请解释下其中的 than previously thought 的语法现象.
答
1. be likely to是词组,有可能的意思,加上more就是更加可能,而harbor相当于have,拥有,心怀的意思.整句意为：遗传学家解释道：近亲结合更有可能产生基因突变,他们的小孩出生便有缺陷的几率更大.2. previously是之前,...为讨论更加深入，请继续回答：1.请问英语中有没有 纯粹be to do(如are ,isto do)这样的句型，如有，情举例并说明下。2.英语中than后面除了跟过去分词（如thought），还可以跟哪些？非常感谢。1.有的。be to do 表示按计划或安排要做的事.When are you to leave for home?2.名词，代词。比如 I am taller than you .I love history better thanmath.