Answer:Four types of vaccines are currently available: Live virus vaccines use the weakened (attenuated) form of the virus. The measles, mumps, and rubella (MMR) vaccine and the varicella (chickenpox) vaccine are examples
Activation energy is the energy needed to begin breaking the bonds of reactants and is denoted as option D.
<h3>What is a Reactant?</h3>
These are the substances which take part in a chemical reaction and result in the formation of the product.
The activation energy is required as it breaks the bonds of the reactant thereby resulting in the product being formed. This therefore makes it the most appropriate choice.
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There are a total of 4 elements
