Rank the hydrogen atoms $(H_a, H_b, H_c)$ present in the following molecule in decreasing order of their acidic strength.

The rate of attack of an electrophile is least when $X$ in the given compound is

Give three points of difference between the inductive effect and the resonance effect.

Given below are two statements:
Statement $I$: In $O_2N-C_6H_4-CH^+-C_6H_4-OCH_3$, the carbocation is stabilised by $+R$ effect of $-OCH_3$ group.
Statement $II$: In $O_2N-C_6H_4-CH^--C_6H_4-OCH_3$, the carbanion is stabilised by $-R$ effect of $-NO_2$ group.
In the light of the above statements, choose the correct answer from the options given below:

Polarization of electrons in acrolein may be written as

Which of the following is not explained by hyperconjugation?