A wooden block is sliding down an inclined plane at constant speed. The magnitude of the frictional force between the block and the plane is equal to a. zero
b. the magnitude of the weight of the block
c. The magnitude of the component of weight of the block parallel to the plane
d. The magnitude of the component of Normal reaction of the block parallel to the plane

Letter a, because when there are unlike charges they will always attract to each other.

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.