What do cells secrete to maintain the proper ph for enzymes to work?
Options:
- (A) Energy
- (B) Chemical energy
- (C) water conservation
- (D) sweating
- (E) heat energy
- (F) aqueous solution
- (G) Organic compounds
- (H) electrolytes
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Let's think first: Cells secrete acids and bases to maintain the proper pH for enzymes to work. Acids and bases are electrolytes. Cells secrete electrolytes to maintain the proper pH for enzymes to work.... So the answer is [(H)]

How do children learn?
Options:
- (A) reusing materials
- (B) allow growth
- (C) by lying
- (D) Riding a bike
- (E) in many ways
- (F) exercise
- (G) by sleeping
- (H) just one way
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Let's think first: Playing is just one of many ways that mammals and other animals learn how to behave. Children learn through play and in other ways. Children and animals learn in many ways.... So the answer is [(E)]

What provides food and shelter to many ocean organisms?
Options:
- (A) houses
- (B) umbrellas
- (C) limestone
- (D) ferns
- (E) sharks
- (F) barnacles
- (G) calcite
- (H) sheds
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Let's think first: Coral reefs provide food and shelter to many ocean organisms. Coral reefs are predominantly calcite. Calcite provides food and shelter to many ocean organisms.... So the answer is [(G)]

What is better able to dissolve oxygen and nutrients than standing water?
Options:
- (A) puddles
- (B) microorganisms
- (C) ponds
- (D) nitrogen
- (E) swamp vegetation
- (F) Veins and arteries.
- (G) streams and creeks
- (H) peachleaf willow
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Let's think first: Running water is better able to dissolve oxygen and nutrients than standing water. Streams and creeks provide running water. Streams and creeks are better able to dissolve oxygen and nutrients than standing water.... So the answer is [(G)]

Energy enters what in the form of sunlight or chemical compounds.
Options:
- (A) biomes
- (B) fire
- (C) light
- (D) Energy.
- (E) Energy
- (F) LEDs
- (G) propagate
- (H) photons
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Let's think first: Energy enters ecosystems in the form of sunlight or chemical compounds. Biomes are global ecosystems. Energy enters biomes in the form of sunlight or chemical compounds.... So the answer is [(A)]

Which item found in the human body is smaller?
Options:
- (A) the eyes
- (B) Epidermis
- (C) all matter
- (D) Fingernail.
- (E) Inches
- (F) Baby tooth.
- (G) Small eyelash.
- (H) Neuron.
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Let's think first: Cells vary in size as well as shape, but all cells are very small. Neurons are cells that are similar to other cells. Neurons are very small in size.... So the answer is [(H)]