Blank is a set of interacting components connected in such a way that a change in one
part affects one or more other parts.
O An
element
A Joule
Water
A system

It’s an Element. Because each of more than one hundred substances that cannot be chemically interconverted or broken down into simpler substances and are primary constituents of matter. Each element is distinguished by its atomic number, i.e. the number of protons in the nuclei of its atoms.