20. After the conditions, I decided not to join the competition. A. know B. to know C. have known D. knowing

Take a look at this dictionary entry. contest con • test (n.) kon-test [from anglo-french or latin] 1. a competition between rivals for a prize 2. a struggle for victory 3. a dispute; controversy (v.) kuhn-test 4. to fight for in a battle 5. to call into question