Biomolecules

Inulin is a polysaccharide of fructose stored as reserve food in the roots and tubers of plants like dahlia and Jerusalem artichoke.
Pectin (pectic compounds) is a polysaccharide found in the middle lamella and cell walls, and can also act as a stored carbohydrate in fruits.
So, in plants, inulin and pectin are reserve materials.

Vitamin E is tocopherol; correctly matched.
Vitamin D is calciferol (not riboflavin); vitamin $B_2$ is riboflavin.
Vitamin $B_1$ is thiamine; vitamin A is retinol.
So the correct match is vitamin E – tocopherol.

Cellulose is the main structural component of plant cell walls; wood is about 50 percent cellulose and cotton about 90 percent.
Because plants make up most of the earth's biomass, cellulose is the most abundant organic compound on earth.
So the most abundant organic compound is cellulose.

Erucic acid is a long chain (C22) monounsaturated fatty acid present in large amounts in mustard and rapeseed oil.
High erucic acid content is considered harmful (it is linked to heart damage in animal studies), so it is used as an indicator of the quality of edible oils; low erucic acid varieties (e.g. canola) have been developed.
So, as per the answer key, spoilage (poor quality) of oil is detected by erucic acid.