What must be done to be certain that a chemical change has taken place?
a. check for the production of bubbles before and after the change.
b. demonstrate that a release of energy occurred after the change.
c. check the composition of the sample before and after the change.
d. demonstrate that energy was absorbed by the reactants after the change.

c. Check the composition of the sample before and after the change.

Explanation:

In a chemical change there is change in the chemical composition. So the chemical composition of the reactants is different than the chemical composition of the products. During a chemical change the bonds in the reactants are broken and new bonds are formed in the products.

a

explanation:

many plants naturally reproduce this way, but it can also be induced artificially. horticulturalists have developed asexual propagation techniques that use vegetative plant parts to replicate plants. success rates and difficulty of propagation vary greatly. monocotyledons typically lack a vascular cambium and therefore are harder to propagate.

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