select the correct answer.
who did the speaker think was "rapping at the chamber door"?
a.
an illusion
b.
a maiden
c.
a raven
d.
a visitor

d) a visitor

Explanation:

As of some one gently rapping, rapping at my chamber door.

'Tis some visitor,' I muttered, tapping at my chamber door —

Only this, and nothing more.'

straight from the story

by using  production possibilities graph.  opportunity costs are key expenses in financial matters and are utilized as a part of registering money saving advantage investigation of a venture. such expenses, be that as it may, are not recorded in the record books but rather are perceived in basic leadership by processing the money costs and their subsequent benefit or misfortune.