I don't think a correction is necessary. Both parts of the sentence are already in the present tense. Plus, the use of "us" in the beginning of the sentence indicates a personal attachment.
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 :)
Id go with the second choice, REPETITION because he says "let both sides" over and over again.
good luckk
