196q: chlorine demand is measured by ?a. horrock’s apparatusb. chlorimeterc. double potd. berkfeld filter answer a . horrock’s apparatus . 197q: in a study in UK they found an association between sale of asthmatic drugs and an increase in deaths due to asthma from 1979 to 1990 . this is an example of ?a. ecological studyb. cohort studyc. case reference studyd. experimental study answer a .