### 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 some people may ask: why the expiration date for bagged milk powder is one year, and that for canned milk powder is two years or even longer?
### Errors: There is a minor error at "that for".

### 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?