The correct statement is:
"Ectotherms cannot insulate (stop heat loss from) their bodies and can only control their body temperature by changing location."
Ectotherms, such as reptiles and amphibians, rely on external environmental conditions to regulate their body temperature, often by changing location (e.g., moving into the sun or shade). They lack the physiological mechanisms (like fur or fat) that endotherms (such as mammals and birds) have to insulate and regulate their body heat.