Which is the best definition of activation energy? the energy required to end a chemical reaction the energy required to bind a substrate to an active site the energy required to form or break the bonds of reactant molecules the energy required to re-form bonds in product molecules

Chalk is an ionic compound. which is a property of all ionic compounds that makes chalkboard? particularly useful for writing on a a high melting point hardness and brittleness inability to dissolve in water a multicolored appearance

Creating new things to solve problems and improve life depends on the close interaction of which two fields?

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?