Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R): 

Assertion (A):	Many amphibians excrete mainly ammonia when they are aquatic tadpoles and switch largely to urea excretion when they become land dwelling adults.
Reason (R):	The main disadvantage of urea is its energy cost and the main advantage is its low toxicity.

In the light of the above statements choose the correct answer from the options given below

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	Both (A) and (R) are False.

Which area actually secretes renin into the blood?

Which of the following is true for excretion in humans?

The hormone produced by the adrenal cortex, when stimulated by angiotensin II, that causes increased sodium and water reabsorption in the distal convoluted tubules, is:

10 to 15 distinct conical or triangular structures in the human kidney are seen in renal ______ and are known as renal ____________.

About what percent of the glomerular ultrafiltrate is reabsorbed by the tubules during urine formation?

The vascular endothelium of glomerular capillaries, basement membrane, and podocytes in the inner lining of Bowman’s capsule form:

The functional unit of the human kidney is the:

Urine from the major calyces in the kidney is collected by:

The presence of which of the following in urine would be abnormal?