Explanation:

- The idiom "hard of hearing" typically refers to someone who has difficulty hearing sounds clearly.

- Option 1: Inaccessible: This means someone or something that cannot be reached or is difficult to approach, and it does not align with the idiom's meaning.

- Option 2: Callous: This refers to someone who is emotionally hardened or unfeeling, which is not relevant to the context of hearing.

- Option 3: Partially deaf: This reflects the reduced ability to hear, which directly relates to "hard of hearing."

- Option 4: Insensitive: This refers to someone who is not empathetic or considerate, unrelated to hearing capability.