Which one of these exhibits a notochord at some stages of its development?

a brittle star

a tapeworm

a cat

a hydra

An atom of sodium-23 (atomic number = 11) has a positive charge of +1. give this information, how many electrons does it have? how many proteins and neutrons does this atom have

An atom of lithium (li) and an atom of chlorine (cl) engage in a chemical reaction. which correctly describes the structure of the resulting chemical compound? hint: consider the class of each element. the chemical compound will have a network structure. the chemical compound will have triple bonds. the chemical compound will have a ball-and-stick structure. the chemical compound will have double bonds.

Explain the relationship between forward and backward reactions in equilibrium, and predict how changing the amount of a reactant (creating a tension) will affect that relationship.