Step 1: Look at what is being asked.
Match each name to the field they are known for. Only one of the four wrote mainly on disability. We will work it out by sorting the choices one at a time.
Step 2: Working through the choices, part 1.
Start by linking each name to the field the person is best known for. Four names, four fields. Then pick the one linked to disability.
Step 3: Working through the choices, part 2.
Phule is linked with caste reform and schools for girls and lower castes. This is the wrong field, so Phule is out.
Step 4: Working through the choices, part 3.
Ellison is linked with race and the novel Invisible Man in the United States. This is the wrong field, so Ellison is out.
Step 5: Working through the choices, part 4.
Ghai is linked with disability, the body and identity in India. This fits the field asked about, so she is in. Rege is linked with caste and gender, so she is out.
Final Answer:
Only one name fits the field of disability, so option 3 is the answer. \[ \boxed{\text{Option 3}} \]