### Chinese: 那么大家肯定会问：为什么袋装保质期是一年，而听装的保质期是两年或更长呢？
### English: Then everyone must ask: Why is the shelf life of bags only one year and the shelf life of cans is two or more years?
### Errors: There is a major error of incorrect translation includes information not present in the correct translation at "everyone must ask". There is a major error of incorrect translation does not accurately represent the correct translation at "bags and cans".

### Improved English: Then you may ask: why is the shelf life of milk powder one year in bags and two years or longer in cans?