$CH_3MgBr + CO_2$ $\xrightarrow{\text{Dry ether}} Y$ $\xrightarrow{H_3O^{\oplus}} Z$. Identify $Z$ from the following.

The electron affinity values of elements $A, B, C$ and $D$ are respectively $-135, -60, -200$ and $-348 \ kJ \ mol^{-1}$. The outer electronic configuration of element $B$ is

If $f: N \rightarrow Z$ is defined by $f(n)=\begin{cases} 2 & \text{if } n=3k, k \in Z \\ 10 & \text{if } n=3k+1, k \in Z \\ 0 & \text{if } n=3k+2, k \in Z \end{cases}$,then $\{n \in N: f(n)>2\}$ is equal to

The slopes of the focal chords of the parabola $y^2=32x$,which are tangents to the circle $x^2+y^2=4$,are

In a reversible isothermal process,the change in internal energy is ...... .

What are the algal components of a lichen called?