I believe the answer is: Unsymphatetic
The word callous is commonly used to describe a person who tend to disregard other people's feeling or condition in their actions.
Callous people usually cannot get in touch with their emotion really well, which make them unsymphatetic to other people's struggle.
The option C is a fused sentence, because its connecting two "parts", "clauses" or "phrases" without being separated from punctuation or other connectives, that should make it a proper sentence. Therefore, we could make various types of changes to turn this fused sentence into a correct sentence:
- Addition of a semi-colon (;)
<em>My dad doesn't have a hobby; He is too busy working.</em>
- Using a subordinate conjunction
<em>My dad doesn't have a hobby because he is too busy working.</em>
- Separating definitely the clauses:
<em>My dad doesn't have a hobby because he is too busy working.</em>
