What commonly ingested substances are absorbed through the stomach wall?

In the practice of science, this type of reasoning is used to develop explanations.

What does polymerase chain reaction (pcr) do? o a. separates dna fragments by size o b. cuts a dna sample into fragments o c. provides an overall picture of a person's chromosomes o d. makes more copies of a sample of dna

What substance acts to prevent sudden ph changes in bodily fluids?