TASK DEFINITION: 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.
PROBLEM: Category: WORLD RIVERS 
Clue: With 4, more national capitals are located on this river than any other river in the world

SOLUTION: the danube

PROBLEM: Category: COMMUNICATIONS 
Clue: The "T" in TASS, an agency founded in the Soviet Union in 1925, stands for this

SOLUTION: telegraph

PROBLEM: Category: 25 YEARS & COUNTING 
Clue: In 2009 she was on a world tour at age 69; when "Jeopardy!" premiered in September 1984, she had the USA's No. 1 hit

SOLUTION:
tina turner