Answer:
c. sensorimotor
Step-by-step explanation:
The stage that your little sister is at is the sensorimotor stage. This stage generally occurs between the ages of 0 to 2. During this stage, babies tend to touch everything that they find, often putting things in their mouths. Babies at this age learn what they need to know about the world by using their senses and interacting with their surroundings. This also allows them develop their fine motor skills.