Which BEST explains why a population of a certain species of cactus developed longer spines over time?

Which statement is best described as a atom

Kc = 0.040 for the system below at 450oc. if a reaction is initiated with 0.40 mole of cl2 and 0.40 mole of pcl3 in a 2.0 liter container, what is the equilibrium concentration of cl2 in the same system? pcl5(g) ⇄ pcl3(g) + cl2(g)

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion