1)当let后只有一个单音节动词,变被动语态时,可用不带to 的不定式。例如:
They let the strange go.他们放陌生人走了。
——> The strange was let go.
2)当let 后宾补较长时,let 通常不用被动语态,而用allow或permit 代替。例如:
The nurse let me go to see my classmate in the hospital. 那护士让我去探望住院的同学。
----> I was allowed / permitted to see my classmate in the hospital.