I am not sure but I think it's c or d. I think the answer is d but I'm not sure so don't take my word for it.
Answer:
Children tend to have this behavior when they are learning about the things around them. This is common with children that are younger than seven months. At this age, they may not be able to explore objects with their hands yet, but are rather only able to grab onto items. Since a baby's mouth has more nerve endings than any other part of their bodies, they tend to see what things feel like with their mouths. Babies usually learn through textures.
Hope this helps :)
They were invaded......................
