Answer:
Sucrose is a disaccharide composed of alpha D gluose and beta D fructose linked together by beta 2,alpha1 glycosidic linkage.
Explanation:
The specificity of glycosidic linkage very much essential to choose the substrate for the synthesis of specific disaccharide.
For example sucrose contain beta 2,alpha1 glycosidic linkage that means the hydroxyl group of anomeric carbon of one monosaccharide(fructose) should remain in beta conformation and the hydroxyl group of other monosaccharide(glucose) should remain in alpha conformation.
1,3-pentadiene has two double bonds which are conjugated, which undergo electrophilic addition reaction on reacting with 
.
The structure of 1,3-pentadiene is shown in the image.
When strong acid such as reacts with 1,3-pentadiene, the electrophilic addition reaction can occur either on double bond at 1,2-position or at 3,4-position. The reaction that occurs is shown in the image.
