They listened to the teacher carefully.这种被动语态直接用过去分词listened

They listened to the teacher carefully.这种被动语态直接用过去分词listened?不应该用is listened?
那主动改成被动语态 The teacher was listened to carefully.这个被动句省略了宾语，那一定要有这个 to 不省略的话是 The teacher was listened to them carefully.貌似也不行吧。
Her voice trembled with excitement.The timid man trembled with fear.
这两个trembled都是过去时吗？这2个颤抖 都不是“被颤抖”吗？
还有之前还看到一道题：
The students listened carefully to the teacher with their eyes -_____on the blackboard (D).
A to focus B focusing C being focused D focused
固定短语：focus one's(their) eyes on sth(the blackboard)，意思是“把某人的目光专注于某事物”，所以固定结构“with + 宾语their eyes + 宾语补足语focus on the blackboard”中，宾语和宾补动词focus之间为动宾/被动关系，所以必须选用其过去分词形式focused.
他这里解释的说是因为是被动语态，才用的focused 这里是因为补语 所以不能用be吗？