6. Which statement best explains a change in the incidence

of disease in 1970?

(1) Children were vaccinated against measles.

(2) New drugs cured diabetes,

(3) The bacteria that cause pneumonia developed a

resistance to drugs.

(4) New technology helped to reduce the incidence of

all three diseases.

(1) Children were vaccinated against measles

Explanation:

correct answer is a) As children were vaccinated against measles            

because as per graph given in attach file                                

by 1940 to 1950 and 1950 to 1960 incidence is increasing

but in 1970 we can see that incidence (diseases ) will be decrease

so we can say here  Children were vaccinated against measles