(a) ${\mathrm{CH}}_2={\mathrm{CH}}_2$                 

(b) ${\mathrm{CH}}_3-\mathrm{C}\equiv \mathrm{N}$

(c) 

(d) 

Which of the above can behave both as an electrophile as well as a nucleophile?

I 

II 

The effect of benzene ring in compound (I) and (II), respectively, will be:

Conjugated double bond is present in:

(a) $1, 2$-butadiene

(b) $1, 3$-butadiene

(c) $1, 3$-pentadiene

(d) $\mathrm{\beta }$-butylene

(e) Benzene