Which of the following statements is correct?

1. The ascending limb of loop of Henle is impermeable to water

2. The descending limb of loop of Henle is impermeable to water

3. The ascending limb of loop of Henle is permeable to water

4. The descending limb of loop of Henle is permeable to electrolytes

The part of nephron involved in active reabsorption of sodium is:

1. distal convoluted tubule

2. proximal convoluted tubule

3. Bowman's capsule

4. descending limb of Henle's loop