If the IRS hasn't raised any issues about your 2005 tax return by now, it is safe to shred it. Last, you should keep any tax return that includes a claim for deducting worthless securities for seven years. If you've lost or discarded a tax return and later need a copy, don't worry.
Rule 2 in the âApostrophesâ section says, âUse the apostrophe to show possession. Place the apostrophe before the s to show singular possession.â. Since âworldâs biggestâ is singular possessive, you need to use âs regardless of which noun follows it.
Ad. 2. Be consistent when you use apostrophes after words that end in s.  When someone's name ends with an s, it is acceptable to use an apostrophe without an s to show ownership, but linguists with the Chicago Manual of Style, along with others, prefer to add an s after the apostrophe.