Which is the sweetest naturally ocurring sugar? 

Fructose 

The correct answer is option 3. Fructose.

Fructose is generally considered the sweetest naturally occurring sugar among the options listed. It is found in various fruits, honey, and some root vegetables. The sweetness of sugars is subjective and can vary from person to person, but, on average, fructose is perceived as sweeter than glucose or sucrose.