To solve this problem, we need to find the highest marks obtained in each subject and then calculate the overall percentage based on these maximum scores.

Step 1: Identify the highest marks obtained by any student in each subject.

• Maths (Max. 150): Highest score is $100$ (Aman).
• Chemistry (Max. 130): Highest score is $80$ (Aman).
• Physics (Max. 120): Highest score is $90$ (Ayush).
• Geography (Max. 100): Highest score is $95$ (Muskan).
• History (Max. 60): Highest score is $90$ (Sajal).
• Computer Science (Max. 40): Highest score is $90$ (Muskan).

Step 2: Calculate the total marks obtained by this student.

• For Maths: $\frac{100}{150} \times 150 = 100$
• For Chemistry: $\frac{80}{130} \times 130 = 80$
• For Physics: $\frac{90}{120} \times 120 = 90$
• For Geography: $\frac{95}{100} \times 100 = 95$
• For History: $\frac{90}{60} \times 60 = 90$
• For Computer Science: $\frac{90}{40} \times 40 = 90$

Step 3: Calculate the total maximum marks possible.

• Total maximum marks = $150 + 130 + 120 + 100 + 60 + 40 = 600$

Step 4: Calculate the total obtained marks.

• Total obtained marks = $100 + 80 + 90 + 95 + 90 + 90 = 545$

Step 5: Calculate the overall percentage.

• Overall percentage = $\frac{545}{600} \times 100 = 90.833\%$

Thus, the correct answer is $90 \frac{5}{6}\%$, which corresponds to option D.

Let me know if you'd like further clarification!

Here are five questions to expand on this:

1. How do we calculate percentages for multiple subjects?
2. Why do we compare the highest scores to the total maximum marks?
3. What would the total marks be if all scores were the lowest?
4. How would the percentage change if one subject's score increased slightly?
5. How is the overall percentage affected by the weight of each subject?

Tip: When working with percentages, ensure that you always use the correct ratio of obtained marks to maximum possible marks for each subject.