Answer:
A. easily combines chemically with other substances.
Step-by-step explanation:
The reactivity is the property of a substance or element to react. They react to be stable which occurs with a low energy state, or for the element when it has 8 electrons in its valence shell. So, a reactivity substance can easily react, or combine chemically with other substances.
To burn in the presence of water, the substance has to be a high combustion enthalpy in the presence of water; to displace the dissolved oxygen, it can't dissolve it well; and to have a high boiling point it must have strong bonds and high molecular weight.