How is the Porter's reaction to the knocking different than the Macbeths' reaction to it in the previous scene?
a) The Porter is indifferent, while the Macbeths are anxious.
b) The Porter is frightened, while the Macbeths are relieved.
c) The Porter is annoyed, while the Macbeths are startled.
d) The Porter is excited, while the Macbeths are calm.