Answer:
The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.
Explanation:
Balancing, running, and jumping are all examples of <em>gross</em> motor skills.
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I quote from Wikipedia:
"Gross motor skills are the abilities usually acquired during childhood as part of a child's motor learning. By the time they reach two years of age, almost all children are able to stand up, walk, jump, run, walk up stairs, etc. etc."
In physical science there are two types of "isolated systems"
1. Being a Physical System in which it is so far removed from other systems that it does not react with any of them.
2. Being a Thermodynamic System in which it is enclosed by rigid immovable walls of which neither mass nor energy can flow through.
I believe in this case although not stated that it would refer to a Thermodynamic System which would leave you with the only plausible answer as ENERGY AND MATTER CANNOT ENTER OR LEAVE.
None of the other answers make sense. Even if it were referring to Physical. Physical does not react with anything at all. An as you can see Thermodynamic does not allow for anything to pass through or leave.
