Consider a variation of CSMA, whereby all stations that overhear an ongoing data exchange transmit a busy tone. The busy tone is transmitted out-of-band so as to not interfere with the data exchange. All stations that hear the busy tone refrain from contending for the medium (keep silent). Such a solution:
(a) Addresses the hidden node problem, but not the exposed node problem.
(b) Addresses the exposed node problem, but not the hidden node problem.
(c) Addresses both the hidden node and the exposed node problems.
(d) Does not address either the hidden or the exposed node problem.
(e) Addresses the near-far problem.