Final answer:
The output signal tc of a 16-bit down-counter requires 16 bits to represent all possible count values.
Step-by-step explanation:
In a down-counter, the terminal count (tc) signal is generated when the counter reaches its maximum count value and transitions from that value to zero. For a 16-bit down-counter, the maximum count value is given by 2^16 - 1 = 65535. Since a 16-bit counter can represent 2^16 different values, the output signal tc will require 16 bits to represent all possible count values.