24. The product that honey bees produce and use it to seal cracks and repair their hives is :
C. Propolis ✔
Explanation :
Bees use propolis to seal cracks and repair their hives.

Answer:
<em>“Eutrophication is an enrichment of water by nutrient salts that causes structural changes to the ecosystem such as: increased production of algae and aquatic plants, depletion of fish species, general deterioration of water quality and other effects that reduce and preclude use”.</em>
Explanation:
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1. Testing only one variable
A controlled variable means its the one that stays the same. In a controlled experiment, it means there is only one manipulated, (changed) variable.
Answer:
Ionic bond
Explanation:
A bond formed by the electrical attraction between two oppositely charged ions is an Ionic bond.