Afood product claiming to be sugar free contains
a. less than 10 grams of sugar per serving.
b. less than 0.5 grams of sugar per serving.
c. less than 5 milligrams of sugar per serving.
d. less than 2 milligrams of sugar per serving.

A food product claiming to be sugar free contains  less than 10 grams of sugar per serving.

Explanation:

There are several sugars, such as lactose (milk), fructose (fruits and honey), maltose (beer), sucrose (table sugar), among others. These can be classified into intrinsic sugar, that is the sugar that is part of the composition of foods such as milk (lactose), vegetables or fruits (fructose) and free sugars, which are those added by manufacturers, consumers or cooks.  This last classification includes sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates.

The main difference between them is that eating a large amount of food containing free or added sugar causes a metabolic reaction that increases the risk of being overweight or obese, and of developing diabetes, gout, ulcerative colitis, vascular diseases and caries. However, the consumption of intrinsic sugars does not pose a health risk.  Therefore, the recommendation of the World Health Organization is that the daily consumption of free sugars should be reduced to less than 10% of the total caloric intake, that is, to a maximum of 25g of free sugars per day.