Step 1: Calculate the total amount spent on purchase.
Aryan bought 100 shares at Rs. 50 each, so the total amount spent on the purchase is:
\[
\text{Total purchase price} = 100 \times 50 = 5000.
\]
He paid a brokerage fee of 2% on the purchase price, so the brokerage fee is:
\[
\text{Brokerage fee on purchase} = \frac{2}{100} \times 5000 = 100.
\]
Thus, the total amount spent on the purchase, including the brokerage fee, is:
\[
\text{Total amount spent} = 5000 + 100 = 5100.
\]
Step 2: Calculate the total amount received on sale.
Aryan sold 100 shares at Rs. 55 each, so the total amount received on the sale is:
\[
\text{Total sale amount} = 100 \times 55 = 5500.
\]
He paid a brokerage fee of 2% on the sale amount, so the brokerage fee is:
\[
\text{Brokerage fee on sale} = \frac{2}{100} \times 5500 = 110.
\]
Thus, the total amount received on the sale after the brokerage fee is:
\[
\text{Total amount received} = 5500 - 110 = 5390.
\]
Step 3: Calculate the net profit.
The net profit is the difference between the total amount received and the total amount spent:
\[
\text{Net profit} = 5390 - 5100 = 290.
\]
Step 4: Calculate the net profit percentage.
The net profit percentage is given by:
\[
\text{Net profit percentage} = \frac{\text{Net profit}}{\text{Total amount spent}} \times 100 = \frac{290}{5100} \times 100 \approx 5.69\%.
\]
Thus, the correct answer is:
\[
\boxed{5.69\%}.
\]