I think it’s A but I’m not sure, if it’s wrong I’m sorry
Answer:
vigorous
Explanation:
As you go down group one of the periodic table, the reactions become and more vigorous.
Luster is the term- means the shininess of the metal
chemical changes occur when a substance combines with another to form a new substance called chemical synthesis or alternatively chemical decomposition into two or more different substances these processes are called chemical reactions and in general are not reversible except by further chemical reactions
