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.
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Question: Category: WORD 
Clue: The word spider comes from an Old English form of this verb, referring to its web-weaving

Answer: spin


Question: Category: MAGAZINES ON THE WEB 
Clue: The website for this defunct mag has the "most amazing collection of professional photography on the Web"

Answer: life


Question: Category: SCIENCE 
Clue: For the radioactive isotope Actinium-227, it's 21.8 years

Answer:
half-life