The fumes of lighted 'incense stick' spread in the whole room due to-​

burning of the incense and air drift in the room

Explanation:  the smoke will automatically rise to the top of the room and then with air drift if would help spread further around the room and spread the smell

  distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

  slope of a graph = change in value of y -axis / change in values of x -axis

  comparing both the equations

    change in value of y -axis = change in position

  change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.

what is the actual question though?