Answer:
B) I
(it was I who swept the class)
Step-by-step explanation:
I happens before the verb "swept"
For example, mine does not work in this one because it can only be used after a noun; "This brush is mine."
myself can be flexible such as being used after pronoun or a verb.
"I did this myself." or "I myself will do this."
me is used after a verb. for example
"the one who swept the class was me."
Hope you understand now.