Which of the following has the lowest melting point?

The number of $5$-digit numbers that are not divisible by $5$ and consist of different odd digits is:

What is the correct relationship between the $pH$ values of isomolar solutions of sodium oxide $(pH_1)$,sodium sulphide $(pH_2)$,sodium selenide $(pH_3)$,and sodium telluride $(pH_4)$?

The value of $\int_{0}^{1} \left( \prod_{r=1}^{n} (x+r) \right) \left( \sum_{k=1}^{n} \frac{1}{x+k} \right) dx$ equals

If $\alpha+\beta=-2$ and $\alpha^3+\beta^3=-56$,then the quadratic equation whose roots are $\alpha$ and $\beta$ is

If the lines $x^2+2xy-35y^2-4x+44y-12=0$ and $5x+\lambda y-8=0$ are concurrent,then $\lambda$ equals