英语句子分析，求教

Question

Digital learning systems now charge students for access codes needed to complete coursework，take quizzes， and turn in homework.
这个句子中，谓语是charge，还是charge for？要是charge for，那students是不是就不能放中间了，所以应该是charge？那for引导的介词短语是不是做宾语？

Answer 1

charge 是谓语
students 是宾语
for access codes是宾语补足语追问

After the expiration of the guarantee, we charge for the replacement parts only.

这句话中charge for 是谓语吗？

是不是charge sb for sth时for sth为宾补，而charge for sth，charge for为谓语，sth 为宾语？

Answer 2

主语：Digital learning systems
谓语：charge somebody for something
宾语：students
后面的needed to complete coursework，take quizzes， and turn in homework.是说access codes的追问

access code是什么成分？