Prolonged and constant use of tobacco can weaken the user's immune system and increase the risk of many diseases.. which of the following diseases can makes the air sac in the lungs less elastic, reducing their ability to absorb oxygen? .
a. chronic bronchitis.
b. emphysema.
c. lung cancer.
d. oral cancer.

Which plan groups foods according to types and indicates how much of each type should be eaten daily for a healthy diet? a.mypyramid plan b.food guide pyramid plan c.dietary guidelines for americans d.dietary pyramid guidelines

[120 total points] (public health) in one of the largest human experiments ever conducted, in 1954 a randomized controlled trial was run to see whether a vaccine developed by a doctor named jonas salk was effective in preventing paralytic polio. a total of 401,974 children (ages 6–9), chosen to be representative of those who might be susceptible to the disease, were randomized to two groups: 200,745 children (the control group c) were injected with a harmless saline solution (a placebo) and the other 201,229 children (the treatment group t) were injected with salk’s vaccine.what was the point of giving saline solution to the children who didn’t get the vaccine? explain briefly.

In the essay section of this assignment make a list of 5 of your favorite physical activities. do you like swimming, rollerblading, riding your bicycle, hiking, or playing a sport? maybe you like to go walking around your neighborhood or around the mall. even dancing to music in your room counts as a physical activity. if you can't think of five activities you like to do, list as many as you can think of and write down things you would like to try in the remaining spaces. now that you've written down some of your favorite activities, set a schedule for when you will participate in these activities. try to do each one at least one time this week for a duration of at least 30 minutes. observe how you feel while you are participating in each activity, directly after you finish with the activity, two hours after the activity, and the day after the activity. do you feel better than you did last week when you weren't as active, or do you feel the same? do you have more energy during the day? can you sleep better at night? do you have the urge to be more active? do you feel more relaxed? record any changes to your mood that occur during this time