Which pair represents isotopes?

a. All of the other answers are correct
b. Oxygen-16 and oxygen-18
c. Uranium-235 and uranium-238
d. 238U and 235U
e. A carbon atom with 6 neutrons and a carbon atom with 8 neutrons

A. All of the other answers are correct

Explanation:

Each pairs are from the same elements, meaning they share the same atomic number but different nucleon number (neutron number + atomic number). Thus, all of the answers are correct.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

chemical digestion occurs in the stomach were hcl and pepsin forms chyme, the mouth in which salivary amylase breaks down starch to form bolus, and the small intestine specifically the duodenum.