The major product for the following reaction is:

In the above reaction,the electrophile is substituted at the meta position only,due to:
$I$. Electron density is more at ortho $\&$ para positions
$II$. Electron density is relatively less at ortho $\&$ para positions
$III$. Electron density is less at meta position
$IV$. Electron density is relatively more at meta position
The correct answer is:

An electrophile $E^{\oplus}$ attacks the benzene ring to form an intermediate $\sigma$-complex. Which of the following $\sigma$-complexes has the lowest energy?

Which of the following statements is not characteristic of free radical chain reaction?

The final product $(B)$ will be:

What happens when a chemical reaction occurs?