Glucose,$Na^+$,and amino acids are actively transported substances,because

Which of the following pairs is incorrect?

Which of the following statement$(s)$ is/are true?
$(1)$ Urine is hypertonic in the distal convoluted tubule.
$(2)$ When the urine passes into the collecting tubule,it becomes hypotonic.
$(3)$ Urine is isotonic in the proximal convoluted tubule.
$(4)$ Urine becomes more and more hypotonic as it passes through Henle's loop.

Draw a labelled diagram showing reabsorption and secretion of major substances at different parts of the nephron.

Loop of Henle is found in

In which segment of the nephron does the conditional reabsorption of $Na^+$ and water occur?