Which of the following dienes contain conjugated double bonds?

Question

Quizplus · Accepted Answer

Conjugated double bonds refer to a sequence of three or more alternating double and single bonds. 
I) H2C=CH-CH=CH2 contains conjugated double bonds (three carbons with alternating double and single bonds)
II) H2C=CH-CH2-CH=CH2 does not contain conjugated double bonds (only two carbons with alternating double and single bonds)
III) H2C=CH-CH=CH-CH3 contains conjugated double bonds (four carbons with alternating double and single bonds)
IV) H2C=CH-CH2-CH2-CH3 does not contain conjugated double bonds (only two carbons with alternating double and single bonds)

Which of the Following Dienes Contain Conjugated Double Bonds