How is gravity an attractive force?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

Plz me ! 1 which of earths spheres contains most of its mass? a atmosphere b hydrosphere c geosphere* d biosphere 2 erosion and weathering are examples of which types of forces? a constructive forces b destructive forces* c gravitational forces d inertia-related forces 3 which of the following statements about earths atmosphere is true? a earths atmosphere contains 78% water vapor which is essentail to life b earths atmosphere contains 21% oxygen c earths atmosphere contains carbon dioxide which all life forms require d earths atmosphere allows radiation from the sun to pass through it and warm earths surface* 4 the strenght of the force of gravity between two objects is determined by which of the following factors? select all that apply a the messes of the objects* b the distance between the objects* c the volumes of the objects d the surface area of the objects 5 earth and moon are kept in there respective orbits due to the influence of a inertia b gravity c gravity and inertia* d neither gravity or inertia if you answer all questions right i will give

Which is true concerning the products and reactants of photosynthesis and cellular respiration? a. the products of photosynthesis are sugars and the reactants of cellular respiration are starches. b. the products of photosynthesis are reactants in cellular respiration. c. oxygen is needed for photosynthesis and is given off in cellular respiration.