Compared to the mass of an so2 molecule, the mass of an o2 molecule is (1) One fourth as great
(2) One half as great
(3) the same
(4) twice as great

One correct reason is:

We do not need to keep every financial document we receive. For tax purposes, comparing the amounts on your W2 form to those on your end of year pay stub would suffice to ensure the information is correct instead of keeping every pay stub from the year.

Some people keep a copy of bills they have paid; after a couple of years, it is safe to assume that there are no problems with your payments and you can discard those copies.

The same is true of your bank statements; after 3 to 5 years, most people throw away old statements. After that much time has passed, if no problems have arisen, it is not likely for one to arise.

If we were to keep every piece of financial information we receive, we would run out of space to keep them. We need to do an occasional purge of these records in order to decrease clutter.