Which sentence contains a shift in subject and voice?
a)
His book was returned to the bin, and then Johnny carried the other books home.
b)
The lake contained garbage that flows through the storm drains.
c)
If a student does not understand the assignment, they should consult the textbook.
d)
He couldn't refuse when offered another helping of dessert; sometimes you just can't resist!
Three of those sentences contain shifts in subject -- a, c, and d.
Only one of them includes a passive AND an active verb in the two clauses. Which one, do you think?