<prompt> According to prevalence criteria for determining xerophthalmia problems given by WHO, following are true for an endemic area:Bitot spot 5 poluation of under 6 yrsConjuctival xerosis 1Conjuctival ulcers 0.05Night blindness 1  <response>: Ans. d Night blindness 1Ref : K. Park 23rd ed. 615, 641, 899Criteria and Prevalence for Determining Xerophthalmia Severity:CriteriaPrevalence at risk Night blindness1 Bitots spot0.5 Corneal xerosiskeratomalacia0.01 Corneal ulcer0.05 Serum retinol5 Refer to previous answer for WHO classification of Xerophthalmia 