Heavy metals that pose health hazards to people and ecosystems _. a. are by-products of agriculture
b. accumulate over time
c. affect organisms quickly. with tragic results
d. are not stored in the body

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.

The  answer is b since it all happens under ground