Final answer:
Chloride is the anion among the given options, while sodium and potassium are cations. Aldosterone primarily affects sodium and potassium ions.
Step-by-step explanation:
The anion in the options provided is c. chloride. An anion is a negatively charged ion. In contrast, sodium and potassium are both cations, which means they carry a positive charge. Chloride (Cl-), however, gains an electron when it becomes an ion, resulting in a negative charge. Therefore, the answer to the question 'Which of the following is an anion?' is c. chloride.
Regarding the effects of aldosterone, this hormone primarily affects the sodium and potassium ions, causing an increase in sodium reabsorption in the kidneys, and facilitating the excretion of potassium. Hence, the two ions most affected by aldosterone are sodium and potassium.