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.

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.