The reactivity of a substance is a blank property

Explanation:

Chemical properties

Chemical properties are properties that can be measured or observed only when matter undergoes a change to become an entirely different kind of matter. They include reactivity, flammability, and the ability to rust. Reactivity is the ability of matter to react chemically with other substances

No it isn't. It's a chemical property.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle