Step 1: Identify what is being asked.
The question asks us to find the incorrect statement about Maslow's Need Hierarchy Theory of Motivation.
Step 2: Recall the core assumptions of Maslow's theory.
Maslow's theory is built on three key ideas: (i) human behaviour is driven by needs, (ii) needs are arranged in a hierarchy from basic physiological needs to higher-level self-actualisation needs, and (iii) a person must satisfy a lower-level need before the desire to satisfy the next higher-level need emerges.
Step 3: Check statement (A).
Statement (A): People's behaviour is based on their needs. This is a foundational assumption of the theory and is completely correct.
Step 4: Check statement (B).
Statement (B): People's needs are in hierarchical order, starting from basic needs to other higher level needs. This is the central idea of the theory and is correct.
Step 5: Check statement (C).
Statement (C): Only a satisfied need can motivate a person. This is the opposite of what Maslow said. According to the theory, a satisfied need no longer motivates a person. It is the unsatisfied need that drives and motivates behaviour. Once a need is met, its motivating power disappears and the person moves toward fulfilling the next unmet need. So, statement (C) is factually incorrect.
Step 6: Check statement (D) for confirmation.
Statement (D): A person moves to the next higher level only when the lower need is satisfied. This is the sequential/hierarchical aspect of the theory and is correct. Since statement (C) contradicts the theory, it is the incorrect statement.
\[ \boxed{ \text{(C) Only a satisfied need can motivate a person.} } \]