What does service meter unit hours mean?

What is the special feature of the C4 plants? What substances does NOT function as a catalyst a. carbohydrates b. cofactor c. coenzyme d. enzyme? Kind of energy provided by volcanic activity? What did a vascular system do for plants size-wise? Which part of a helium atom is positively charged? Which would be heavier a pound of bricks or a pound of paper clips? How much does it cost to get in freeze? Is surface tension a physical or chemical property? Which part of the ecosystem is alive and provides oxygen for animals? How are the proteins used for active transport different from those used for facilitated diffusion? What groups of atoms are bonded to carbon chains? When was trepanning used? How long will it take to freeze to death on Pluto? What is the benefit of a solid agar medium? Is a counterexample of all planets have moons? What material is made of oxygen and silicon when magma flows slow? Can you track a sat nav or iPad in anyway if it has been stolen? Are animals that eat meat carnivores? What layer of sun that have eruptions that occur when the loops in sunspot regions suddenly connect? What is industrial disaster?