The correct answer is: Only assumption I is implicit.
The statement “Please do not wait for me, I may be late, start taking lunch as soon as the guests arrive.” is a message from a Director of a Company to his office managers. The Director is asking his office managers to start taking lunch as soon as the guests arrive, even if he is not there yet. This suggests that the Director does not want his guests to wait for him. This is because keeping guests waiting is not desirable.
The statement does not provide any information about whether or not lunch may be ready in time. Therefore, assumption II is not implicit.
Only assumption I is implicit in the statement.