Explanation

(a) When, n-p-n transistor is used as a common base amplifier, the emitter-base input circuit is forward biased and collector-base output circuit is reverse biased.
When $i_{E},i_{B},i_{C}$ are emitter, base and collector current.
The arrow from base to emitter represents the direction of hole current that is the conventional current which is opposite to direction of electron current. Thus, electrons move from emitter to base.