Concept:Development is not fixed but can be changed through interaction with the environment. Explanation:Development includes qualitative and progressive changes in structure, thought, or behavior. It is influenced by both heredity and environment. Development is a lifelong process that continues gradually. It is modifiable, meaning new structures and functions emerge from interactions with the environment. Development follows a predictable pattern but is not unidimensional or uni-directional. It involves multiple dimensions (physical, emotional, social) and directions (gains and losses). Development is not totally genetically pre-programmed; environment plays a key role. The formula Development=Heredity×Environment shows both factors matter. Hence, development is modifiable. Answer:C. modifiable.