3. (10 points) Two cyclists are training on different tracks. Cyclist $A$ uses a circular track, with a diameter of 1 kilometer; Cyclist $B$ uses a straight track, with a length of 5 kilometers. Cyclist $A$ completes 3 laps in 10 minutes, while Cyclist $B$ travels 2 round trips in 5 minutes. What is the ratio of the speed of Cyclist $A$ to the speed of Cyclist $B$? ( )
A. $1: 1.6 \pi$
B. $\pi: 10$
C. 3: 4
D. $3 \pi: 40$
【Analysis】Through analysis, we can know; the speed of $A$ is: $\pi D \times 3 \div 10=\pi \times 1000 \times 3 \div 10=300 \pi$ (m/min)
The speed of $B$ is: $5000 \times 2 \times 2 \div 5=4000$ (m/min)
The speed ratio is: $A: B=\pi \times 1000 \times 3 \div 10: 5000 \times 2 \times 2 \div 5$, solve accordingly.
【Solution】Solution: From the data in the question, the speed of $A$ is: $\pi D \times 3 \div 10=\pi \times 1000 \times 3 \div 10=300 \pi$
(m/min)
The speed of $B$ is: $5000 \times 2 \times 2 \div 5=4000$ (m/min)
The speed ratio is: $A: B=300 \pi: 4000$
$$
=3 \pi: 40
$$

Therefore, the answer is: D.