Low-fat, low-cholesterol, and dairy-free diets are all diets that are necessary for

D. health reasons

Explanation:

A low fat and low cholesterol diet are essential for the human body and this diet as one should limit one's consumption of fats and oils and avoid the usage of butter and coconut oil and use of the homemade oils as they do not contain any preservatives or added flavors and thus are god for health. And as a precaution, one should read on the ability of the product their contents and there are saturated and unsaturated fats that are present in the animals and take ess of animal proteins.

The figure is not necessarily a parallelogram because only one diagonal is bisected and only one pair of sides is congruent.