Step 1: Henle's loop ના ભાગ.
Henle's loop: descending limb (DL) = water permeable, electrolytes impermeable. Ascending limb (AL) = water impermeable, electrolytes actively/passively transported.
Step 2: Statements ની ચકાસણી.
(a) DL water-permeable, electrolytes impermeable - correct. (b) Henle's loop માં urine concentrate થાય છે - correct. (c) Na+ AND water reabsorption - wrong; AL માં water impermeable છે. (d) AL માં electrolytes active/passive transport - correct.
Step 3: સાચો ઉત્તર.
\[ \boxed{(a),\ (b)\ \text{and}\ (d)} \]