Car X traveled 3d distance in t time. Car Y traveled 2d distance in t time. Therefore, the speed of car X, is 3d/t, the speed of car Y, is 2d/t. Since speed is the distance taken in a given time.
In figure-2, they are at the same place, we are asked to find car Y's position when car X is at line-A. We can calculate the time car X needs to travel to there. Let's say that car X reaches line-A in t' time.

Okay, it takes t time for car X to reach line-A. Let's see how far does car Y goes.

We found that car Y travels 2d distance. So, when car X reaches line-A, car Y is just a d distance behind car X.
The correct answer is:
D. Electromagnetic waves.
The arrows represent electromagnetic waves.

Subjective questions can be answered most likely through well-designed scientific investigations. Investigating peoples opinions or favorites does not involve any scientific investigations.
<h3>What are scientific investigation?</h3>
Scientific investigations include study on different natural phenomenon through well designed research methodologies. They include a preliminary hypothesis based on observations and various scientific records helps for reference.
Through well designed scientific experiments we can solve subjective questions and can be helpful in solving different environmental or social issues.
Peoples opinion or objective types questions are not targeted at scientific investigation, hence, option b is correct.
To find more on scientific investigations, refer here:
brainly.com/question/8386821
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