Answer: The correct option is, It is a line joining the points whose x and y coordinates add up to 4.
Explanation:
The given equation is,

when we take x = 1 then


when we take x = 2 then


From this we conclude that the sum of 'x' and 'y' coordinates is always equal to 4.
Hence, the correct answer is, It is a line joining the points whose x and y coordinates add up to 4.