You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: "R"ITERS 
Clue: This author of the hitchhiking novel "Even Cowgirls Get the Blues" once hitchhiked across the U.S.
tom robbins

Category: PRESIDENTS 
Clue: Though only 5'7", this founding father was called "The Colossus of Independence"
john adams

Category: E-COMMERCE 
Clue: alzheimersupport.com is among sites offering this super-herb, the scientific name of the maidenhair tree

gingko biloba