Which of the following is a Lewis acid?

The inverse point of $(1,2)$ with respect to the circle $x^2+y^2-4x-6y+9=0$ is

If $y=(1+x)(1+x^2)(1+x^4) \dots (1+x^{2^n})$, then the value of $\left(\frac{dy}{dx}\right)_{x=0}$ is

The specific resistance (resistivity) of material $B$ is twice that of material $A$. The diameter of a circular wire made of $B$ is twice that of a wire made of $A$. If the resistances of both wires are equal,then the ratio of their lengths $l_B/l_A$ will be .......

The angle between the tangents drawn from the point $(1,4)$ to the parabola $y^2=4x$ is

In the expansion of $(1 + x)^n$,the coefficients of the $p^{th}$ and $(p + 1)^{th}$ terms are respectively $p$ and $q$. Then $p + q = $