Final answer:
The word 'treatable' means that a condition or situation can undergo treatment, which is reflected in choice d. can be treated.
Step-by-step explanation:
The correct definition for treatable is d. can be treated. The suffix 'able' in English often implies that something is capable of being done. In this case, the word 'treatable' refers to a condition or situation that is capable of receiving treatment, implying that there is a possibility of improvement or cure. Therefore, 'treatable' does not mean without treatment, not treated, or the act of being treated, but rather that the condition can undergo treatment.