Negative inductive effect ($-I$ effect) is shown by:

The total number of contributing structures showing hyperconjugation (involving $C-H$ bonds) for the following carbocation is

Match List-$I$ with List-$II$:
| List-$I$ (Mechanism steps) | List-$II$ (Effect) |
| :--- | :--- |
| $(A)$ Aniline resonance structure | $(I)$ $-E$ effect |
| $(B)$ Electrophilic addition of $H^+$ to alkene | $(II)$ $-R$ effect |
| $(C)$ Nucleophilic addition of $CN^-$ to alkene | $(III)$ $+E$ effect |
| $(D)$ Nitrobenzene resonance structure | $(IV)$ $+R$ effect |
Choose the correct answer from the options given below:

Which of the following is observed in the $C_2H_4$ molecule?

Mesomeric effect involves

Which of the following groups does not show $(+R)$ effect?