For high-quality cement, the lime to oxide ratio must be within the range of 1.9–2.1, ensuring good binding properties and durability
The quality of cement is assessed based on the ratio of lime (CaO) to the sum of oxides (SiO2, Al2O3, and Fe2O3). The formula for this ratio is:
Ratio = \(\frac{\% \text{CaO}}{\% \text{SiO}_2 + \% \text{Al}_2\text{O}_3 + \% \text{Fe}_2\text{O}_3}\)
For good quality cement, this ratio lies in the range of 1.9 to 2.1, which ensures the proper strength and binding properties of the cement. If the ratio deviates significantly:
Conclusion: Since the ratio is closest to 2, the correct answer is 2.
Method used for separation of mixture of products (B and C) obtained in the following reaction is: 
Consider an A.P. $a_1,a_2,\ldots,a_n$; $a_1>0$. If $a_2-a_1=-\dfrac{3}{4}$, $a_n=\dfrac{1}{4}a_1$, and \[ \sum_{i=1}^{n} a_i=\frac{525}{2}, \] then $\sum_{i=1}^{17} a_i$ is equal to
