Recent years, there has been an evidence that the prevalence and intensity of the caries attack has been diminishing in the more economically developed countries

Recent years, there has been an evidence that the prevalence and intensity of the caries attack has been diminishing in the more economically developed countries, mainly because of the wide spread use of:
a. Artificial water fluoridation.***
b. Fluoride toothpaste
c. Dental health education programs
d. A & c.