1) lemon is an example of  _______ a) Acid b) Base c) Neutral 2) A substance of pH of 7 is a) Acid b) Base c) Neutral 3) What is an element? a) The most basic unit of matter b) A compound made of one or more atoms c) A pure substance made of only one kind of atom  d) A special material found in the atmosphere 4) the element needed by humans for breathing a) nitrogen b) oxygen c) carbon dioxide d) methane

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