Select the correct option:-

​      

1. resonating structures

2. tautomers

3. geometrical isomers

4. optical isomers

Which of the following $\mathrm{\sigma }$-bonds participate in hyperconjugation?

Choose the correct statement among the following: 

The correct stability order of following species is :

(1) x > Y > w > z

(2) y > x > w > z

(3) x > w > z > y

(4) z > x > y > w

Which of the following does not represent the resonating structure of

1. 
2. 
3. 
4.