Step 1: Understanding Dialysis
Dialysis is a medical procedure used to filter waste products and excess fluids from the blood when the kidneys are not functioning properly. This process is related to the excretion function of the body.
Step 2: Why Other Options are Incorrect
- (A) Nutrition: Dialysis is not related to the absorption of nutrients.
- (B) Respiration: It is not related to the breathing process or gas exchange.
- (D) Transportation: Dialysis does not involve the transport of substances but is focused on waste removal.
Thus, the correct answer is (C) to excretion.

$PQ$ is a chord of length $4\ \text{cm}$ of a circle of radius $2.5\ \text{cm}$. The tangents at $P$ and $Q$ intersect at a point $T$. Find the length of $TP$.