Which of the following statements are true about urine formation?

(i) The tubular epithelial cells in different segments of nephron perform reabsorption either by active or passive mechanisms.

(ii) Substances like glucose, amino acids, Na + , etc., in the filtrate are reabsorbed passively.

(iii) Nitrogenous wastes are absorbed by active transport.

(iv) Nitrogenous wastes are absorbed by active transport.

(v) Reabsorption of water also occurs passively in the initial segments of the nephron.

(vi) During urine formation, the tubular cells secrete substances like H + , K + and ammonia into the filtrate.

(vii) Tubular secretion helps in the maintenance of ionic and acid base balance of body fluids.