I need some help. The last attempt, I tried A, but it was incorrect.
Two students below described a part of Earth's middle layer:

Bob: The deepest part
Joe: The semi-fluid part

Which part of the middle layer did Bob and Joe describe? (4 points)

Select one:
a. They both described the mesosphere. (Incorrect)
b. They both described the asthenosphere.
c. Bob described the mesosphere and Joe described the asthenosphere.
d. Bob described the asthenosphere and Joe described the mesosphere.