Answer: Sensitive
Explanation: The sensitive period describes an epoch in the development stage of a child which is characterized by rapid, subconscious change in a child's cognitive, physical and psychological capabilities.
Basic developmental characteristics in human are established during these sensitive period such as Language and certain physical changes. During the sensitive period for language development, a child can learn any language frequently spoken within his environment. Environmental factors and conditions contribute very efficiently to a child's development during the sensitive period.