What are THREE ways that living conditions were so bad that they affected the public health before the 1900's.

Ab+cd-> ad+bc is what kind of reaction

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny.i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dancer so i get cardio a lot)

Which describes the effect of prolonged stress on blood pressure? it causes blood pressure to decrease. it has little or no effect on blood pressure. it causes the heart to pump with more force. it causes blood pressure to increase.