You do not want to experience the APEX CPU time limit exceeded message. There are different considerations that you should do. First is letter B. You can use maps for cache so that you can work faster and you can find what you are looking for in a short amount of time. Another answer is C.
You need to avoid repeating the process again and again. If you would do these two options, it is likely that you do not need to be alerted if you have exceeded the time because you will finish before time is up. Time is always important not only in programming but also in other aspects of life.