Correct Answer: Rs. 1,500

Solution : Let the total amount of money that Nakul had be $x$
First, Nakul used 20% of his money to buy wheat flour.
This means he spent $\frac{20}{100}x$ on wheat flour, leaving him with $\frac{80}{100}x$.
Next, Nakul spent 25% of the remaining money on cooking oils.
Amount spent = $\frac{25}{100} \times \frac{80}{100}x$
Therefore, the amount of money left after this expenditure is $\frac{75}{100} \times \frac{80}{100}x$.
According to the given information, Nakul is left with Rs. 900, so we can set up the equation:
$\frac{75}{100} \times \frac{80}{100}x = 900$
⇒ $x = \frac{900 \times 100 \times 100}{75 \times 80}$
⇒ $x = 1500$
Therefore, the total amount of money that Nakul had is Rs. 1500.
Hence, the correct answer is Rs. 1,500.