Which observation most likely indicates that only a chemical change has taken place A. States of matter change

B. The change cannot be reversed(my answer)

C. A reaction occurs

D. The shape changes

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom

Your awser would be a acetone