Some autotrophs/producers are: Wheat Fungi Algae Cacti Trees Shrubs They are made autotrophs because they can produce their own food.
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Friction is important for all sports. Without it it becomes really hard to accelerate or deaccelerate. For example a 100m sprinter. It would be great for him if there wasnt any air resistance...
Both are acceptable, depending on context. For example: Fishing bait is useful to fisherman. Fishing bait is useful for catching fish.
an autotroph is an organism capable of synthesizing its own food from inorganic substances, using light or chemical energy.