2. Xiaoming's home is 30 minutes away from school by subway, and 50 minutes by bus. One day, Xiaoming first took the subway and then transferred to the bus, and it took him 40 minutes to get to school, with the transfer process taking 6 minutes. So, how many minutes did Xiaoming spend on the bus that day? 
(A) 6
(B) 8
(C) 10
(D) 12
Analysis: Method one: Unit "1" and assumption method, assume the distance from Xiao Ming's home to school is "1", the subway speed is $\frac{1}{30}$, the bus speed is $\frac{1}{50}, 40-6=34$ minutes, assuming the entire journey is by subway, it can cover $\frac{1}{30} \times 34=\frac{17}{15}$, so the time spent on the bus is $\left(\frac{17}{15}-1\right)$ $\div\left(\frac{1}{30}-\frac{1}{50}\right)=10$ minutes.
Method two: Numerical method and assumption method, assume the distance from Xiao Ming's home to school is $[30,50]=150 \mathrm{~m}$, the subway speed is $150 \div$ $50=3 \mathrm{~m} / \mathrm{min}$, the bus speed is $150 \div 30=5 \mathrm{~m} / \mathrm{min}, 40-6=34$ minutes, assuming the entire journey is by subway, it can cover $5 \frac{1}{30} \times$ $34=170 \mathrm{~m}$, so the time spent on the bus is $(170-150) \div(5-3)=10$ minutes.
Method three: Time ratio and proportion. For the same segment of the journey, the time ratio of taking the subway to taking the bus is $3: 5$, the entire journey by subway takes 30 minutes, and if part of the journey is by bus, it takes $40-6=34$ minutes, so the segment by bus takes $34-30=4$ minutes more than by subway, so the time spent on the bus is $4 \div(5-3) \times 5=10$ minutes.
The answer is $\mathrm{C}$.