I think your best choice would be a, but it can very well be d.
Answer:
c. occurring at the same time
Explanation:
simultaneously means to do at the same time and c is the only answer choice that reflects this
Indefinite. This should be correct but let me know if I'm wrong
Let's say that a clock is broken, so stuck on the time 6:15. While most of the day, that clock is incorrect, it is correct at 6:15 AM and 6:15 PM, thus it is right twice a day.