The best evidence that there is a critical period for language acquisition is the fact that: a. infants babble sounds that occur in their parents' native language.
b. toddlers maintain a capacity to discriminate language sounds they have never heard.
c. people most easily master the grammar of a second language during childhood.
d. preschoolers typically fail to use proper syntax.

I say the answer is : C. people most easily master the grammar of a second language during childhood.

early settlements on the subcontinent. both the indus and the ganges rivers carried rich silt from the mountains to the plains. when the rivers flooded, the silt spread over the plains and made the soil in the river valleys fertile for farming.

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.