John is participating in an experiment that is designed to determine how much brighter a light has to be before he perceives the magnitude as twice as bright as the original light. jane is participating in an experiment to determine how strong an odor has to be before she initially perceives the odor. the experiment in which john is participating relates to the question and the experiment in which jane is participating relates to the question.

Answerinternal combustion engine fuel;

The answer is: c. from underground

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.