Timing using a TM990 micro-computer: A. require an external timer added by the user B. is available on the standard CPU board C. can be handled in software D. both (b) and (c) E. None of the above.

The correct answer is D. Both (b) and (c).

The TM990 micro-computer has a built-in timer that can be used to generate interrupts at regular intervals. This timer can also be used to measure the elapsed time between two events. In addition, the TM990 micro-computer can also use software to generate interrupts at regular intervals. This is useful for tasks that do not require high precision timing, such as updating a display or controlling a motor.

Option A is incorrect because the TM990 micro-computer has a built-in timer. Option B is correct because the TM990 micro-computer has a built-in timer. Option C is correct because the TM990 micro-computer can use software to generate interrupts at regular intervals. Option E is incorrect because both options B and C are correct.