Scientists often use controlled experiments to answer questions. Choose ALL correct statements about controlled experiments. A) No changes are made to a test group in an experiment. B) A control group is used for comparison to other groups. C) Only one change can be made per test group in an experiment. D) Changes can only be made to the control group in an experiment. E) A controlled experiment must have a control group and test group(s).

Answer is in the photo. I can only upload it to a file hosting service. link below!

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explanation:

covalent bonds

consist of pairs of electrons shared by two atoms, and bind the atoms to fixed orientation and requre high energies to break them

ionic bonds

when two atoms differ considerably in their electronegativity, then one of the atoms will lose its electron to the other atom. this results in a positively charged ion(cation) and a negatively charged ion (anion)

idk i’m struggling too