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 consistency, answers should be in all lower cased letters.
PROBLEM: Category: IT'S NOT SO 
Clue: Though 4,500 miles long, it's not visible from space, as its materials are similar in color to the surrounding soil

SOLUTION: the great wall of china

PROBLEM: Category: UNITS OF MEASURE 
Clue: The scale on the bottom of a sextant is in these units

SOLUTION: degrees

PROBLEM: Category: BARELY ALIVE 
Clue: Defined as asystole, no cardiac electrical activity on the EKG is also known by this "level" term

SOLUTION:
a flatline