Answer: All of the above
Step-by-step explanation:
The options include:
a. Face-to-face
b. Telephone
c. Electronic mail
d. All of the above
Since the manager manager has a message for Bob, any of the communication channels given here can be used.
There is no preferred communication channel here. The manager may decided to tell Bob the message face to face when he sees him. Also, he can call him on the telephone or send an email to him.
Therefore, the correct option is All of the above.