Step 1: Understanding the conditions C or F scores the highest: In every test, either C or F is the highest scorer. Whenever C scores the highest, E scores the least. Whenever F scores the highest, B scores the least. All the students have different marks. D scores higher than A, but they are close competitors: So, D is ranked above A, but only by a small margin. A scores higher than B: A is ranked above B. C scores higher than A: C is ranked above A. Step 2: Analyzing the scenario where F is second If F stands second in the ranking, let's deduce the possible order.

F is second: According to the conditions, F cannot be the lowest scorer. So, the rest of the positions should be filled accordingly. C or F scores the highest: Since F is second, C must be the highest scorer. Whenever C scores the highest, E scores the least: Since C is the highest, E must be ranked last (sixth). D scores higher than A, but they are close competitors: So, D is ranked above A, but close to A. A scores higher than B: A is ranked higher than B. Step 3: Ranking based on conditions Given that C is the highest and F is second, the positions of the students are:

C is first (because C scores the highest). F is second (given in the problem). D is third (since D is higher than A and close competitors with A). A is fourth (since A is higher than B, but lower than D). B is fifth (since A is ranked above B, and B cannot be last). E is sixth (since E scores the least when C is the highest). Step 4: Conclusion The position of B is fifth.

Thus, the correct answer is: C. Fifth.