Which one of the following elements reacts with steam?

Rutherford’s scattering experiment is related to the size of the

Oxyacids of chlorine show similarity in:

If $x_n = \cos \left(\frac{\pi}{4^n}\right) + i \sin \left(\frac{\pi}{4^n}\right)$,then the product $x_1 x_2 x_3 \ldots \infty$ is equal to

If the coefficients $a$ and $b$ of a quadratic expression $x^2+ax+b$ are chosen from the sets $A=\{3,4,5\}$ and $B=\{1,2,3,4\}$ respectively, then the probability that the equation $x^2+ax+b=0$ has real roots is

The equation $(2p-3)x^2 + 2pxy - y^2 = 0$ represents a pair of distinct lines: