What are some possible reason of epidemic in 1989-1991?

People were probably not getting vaccinated or the bacteria became immune to the vaccine.

Explanation: yw plz mark brainliest i need one more (:

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.