Someone !

what must be true for any endothermic reaction?

the chemical bonds of the products have more energy than the chemical bonds of the reactants.

there are more products than there are reactants.

there must be a phase change from solid to liquid or from liquid to gas.

the reaction must take place in a sealed container held at constant volume.

The best and most correct answer among the choices provided by your question is the first choice or letter A "The chemical bonds of the products have more energy than the chemical bonds of the reactants."

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings; usually, but not always, in the form of heat.

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Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.