The table shows the percentage of users of a data tablet who returned the product to an Internet provider within a year after purchase, after a year, and the reasons for the return.

Battery life Monthly service fee New version Totals
Within a year 5% 25% 60% 90%
After a year 1% 3% 6% 10%
Totals 6% 28% 66% 100%
The events of "battery life" and "monthly service fee" are____.

conditional and independent events
conditional and dependent events
dependent events
independent events