Read the excerpt.

my heart aches and drowsy numbness pains
my sense, as though of hemlock i had drunk,
or emptied some dull opiate to the drains
one minute past, and lethe-wards had sunk:
’tis not through envy of thy happy lot,
but being too happy in thine happiness,—
in these lines from verse i of “ode to a nightingale” by john keats, why does the speaker say he feels as though he has taken drugs that make him drowsy and numb?

a. seeing the nightingale makes him envious.
b. he actually has taken drugs that make him feel drowsy and numb.
c. the beauty of the song overwhelms him with joy.
d. hearing the nightingale makes him suicidal.