Final answer:
The prefix "Achy-" does not describe speed or frequency; it is likely a typo in the question. Assuming a correct prefix, 'slowly' would be the adverb indicating something is happening at a slow pace.
Step-by-step explanation:
The prefix "Achy-" is not commonly used to describe speed or frequency in English. Therefore, the information provided in the question seems to be incorrect or a typo. If we assume that the prefix "achy" is a typographical error and perhaps the intended prefix is "achy-" derived from the Greek root "ach" which means "pain" as in 'achy muscles', then none of the options provided (A) Slowly, (B) Normally, (C) Fast, (D) Regularly correspond with the meaning of the prefix. However, if we consider a different question altogether, such as the use of adverbs to describe actions, the correct adverb from the options provided that denotes something happening in a slow manner would be 'slowly'.