Why is a new flu vaccine made every year?

Consider the four elements above. which one of these elements will combine with oxygen in a 1: 1 ratio?

3.09 lab: reaction of metals 1 which combinations of substances resulted in a chemical change? for each metal that participated in a chemical change, write the type of metal it is, based on your examination of the periodic table. were there any metallic compounds that did not react with either the acid or the base? write the type of metal, based on your examination of the periodic table. make a general statement about the reactivity of the metals in this experiment.

Which item is most likely part of the safety contract