Acidic solutions contain high concerntrations of

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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)

to improve her experimental investigation, dalila should add a row in which no fertilizer is used. by a having a contrasting row in which no fertilizer is used, she will have a control group that will her understand the effects of the fertilizer in the plant developments vs the development of the plant when no fertilizer is used.