Final answer:
Malnutrition during critical periods has irreversible effects.
Step-by-step explanation:
The statement is true. Malnutrition during critical periods, such as implantation or organ development, can have irreversible effects. During these periods, the fetus or organs are developing rapidly, and proper nutrition is crucial for normal growth and development. Lack of essential nutrients during these critical periods can result in long-term health issues and developmental abnormalities that cannot be fully reversed even with proper nutrition later in life.