Final answer:
The statement regarding multicellular organisms' internal environment is true, emphasizing the importance of interstitial fluid for life-sustaining exchanges and maintaining homeostasis.
Step-by-step explanation:
The statement 'the internal environment of a multicellular organism is the fluid surrounding cells, through which life-sustaining exchanges are made' is true. The fluid surrounding cells in a multicellular organism is known as interstitial or extracellular fluid. This fluid is crucial for the exchange of nutrients, gases, and wastes between cells and their external environment. It serves as a medium that helps maintain homeostasis within the body. Homeostasis involves various physiological processes that balance the internal conditions with the external environment.
Moreover, in biology, we learn that growth, reproduction, and dynamic homeostasis require cells to create and maintain internal environments that are different from their external environments. This internal regulation ensures that cells can function properly despite changes in the external environment. In this context, 'false' would not describe the statement given about the internal environment of multicellular organisms.