Answer:
The brain and the spinal cord are wrapped in three protective layers of tissue called the meninges. The cerebral spinal fluid goes between these layers to provide more cushion and protection. It nourishes and protects the nerve tissues of the brain and spinal cord. It also acts as a shock absorber, considering humans move a lot and fall.
Newton proved that the force that causes, for example, an apple to fall toward the ground is the same force that causes the moon to fall around, or orbit, the Earth. This universal force also acts between the Earth and the Sun, or any other star and its satellites. Each attracts the other.
The right answer is excess carbon dioxide.
For a cell to do a photosynthesis, it needs.
chloroplast
water (providing hydrogen and oxygen)
Carbon Dioxide (Providing Oxygen and Carbon)
And finally the sunlight.
This will produce, oxygen and glucose, two essential elements in animal life.
I believe its methane and carbon dioxide.... hopefully this works:)