What is the primary distinction between an observational and an experimental analytic epidemiology study? (a) researchers randomly allocate study participants to exposure or non-exposure group(b) its focus is to identify and quantify causal relationship between an exposure and an outcome(c) measures of association is rr or rd researchers decide the level of exposure among participants(d) researchers decide the level of exposure among participants(e) it require follow up of participants to ascertain the occurrence of disease of interest

i'm not sure, but can you answer my most recent question?

answer188 to 210 calories;

when in a crucial situation, after calling 911, the correct posture for delivering effective compression is the proper hand placement.

first, place two fingers at the sternum, then put the heel of your other hand next to the fingers and place hand on top of the other. lock your elbows by using your body’s weight and compress the victim’s chest with a depth of 2 inches.

moreover, do 15 compression and 2 breaths, this process must be done four times until there is a pulse or a arrive.