Answer:
The correct answer is (d) email.
Step-by-step explanation:
Email is a form of written communication between people through digital tools. Also called email or e-mail (for its meaning in English electronic mail), it is one of the most popular means of digital communication and can be used by anyone who has access to the internet.
In this case, Bob must use a means of communication that ensures that he will not interrupt his boss's meeting. In addition, it is practical because an immediate response can be given without having to pass authority filters.