Answer:
The answer is a Carbohydrate!
Rain forests are huge carbon sinks, as plants and trees actively remove carbon dioxide from the atmosphere and store the carbon in biomass. This is a vital ecosystem service for counteracting climate change. Forests regulate the climate, as evapotranspiration from forests influence precipitation patterns and the temperature. Many as yet underdiscovered plants may be of benefit to us as sources of useful products or drugs. Rain forests act as a refuge for vulnerable plant species, thereby protecting them from human over-exploitation and saving biodiversity for future human generations.
The correct answer is d. spinal cord.
Spinal cord is a bundle of neurons which starts from the brain and runs down the entire length of the back of the body. The spinal cord acts as a main means to transmit the messages between the brain and the body.
Sensory or efferent neurons carry the information from the perimeter of the body and pass to the central nervous system whereas the motor or efferent neurons act as a communication channel and carry the information from the nervous system to various glands and muscles.