Renin-angiotensin-aldosterone system secretes mineralcorticoids. These are the steroid hormones. They regulate the water and electrolyte balance in the body. The main mineralocorticoid present in our body is aldosterone.Whenever \\\\(K^+\\\\) concentration rises or \\\\(Na^+\\\\) concentration falls, the aldosterone is released. It stimulates the renal tubules to absorb \\\\(Na^+\\\\) and water and excrete \\\\(K^+\\\\) and phosphate ions from the body. The aldosterone causes the active uptake of \\\\(Na^+\\\\) ions from the nephric filtrate by acting over distal convoluted tubules and collecting tubules. As the sodium concentration in blood restores due to the action of aldosterone, the water also follows it by osmosis, so blood volume is restored. Thus, aldosterone maintains the electrolyte balance, body fluid volume, osmotic pressure, and blood pressure of the body.So, the correct answer is option A.