"I opened the door."
a)The door was opened.
b)The door was opened by me.
Are the two options correct? Is the agent required in this sentence?
"I opened the door."
a)The door was opened.
b)The door was opened by me.
Are the two options correct? Is the agent required in this sentence?
As commented by @user178049, both sentences in the passive are correct.
In the passive voice, you can omit who the doer is. But if you want to focus on the doer, you can add by + the doer.