The duct of Bellini opens into the ........ .

The following figure shows the human excretory system. Identify $P$ and $Q$.
$P \quad Q$

In which of the following is the minimum content of urea present?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Nephrons are of two types: Cortical and Juxta-medullary,based on their relative position in the cortex and medulla.
Reason $R$: Juxta-medullary nephrons have a short loop of Henle,whereas cortical nephrons have a longer loop of Henle.
In the light of the above statements,choose the correct answer from the options given below:

State the location of the kidneys.

Draw a neat and labelled diagram of an excretory unit (nephron).