Question

Which sentence is correctly hyphenated?

Answer 1

C) the twentieth-century had the most tornados on record

Answer 2

D. The hikers spotted a red-tailed pheasant.  

Red modifies tail, not pheasant because the hikers spotted a pheasant with a red tail, not a red pheasant with a tail. When "a noun + an adjective" becomes a compound adjective, you need to use a hyphen.