First you need to add all the fractions you know. 3/12 + 1/12 = 4/12. Then you subtract your answer of 4/12 to 1/2. But you first need a common denominator. A common factor is 12 for example. 4/12 stays the same, but 1/2 becomes 6/12. 6/12, or 1/2 minus 4/12 is 2/12. Your answer is 2/12 or B.
Answer:
B. Case-Control
Explanation:
A case-control is a study that compares a group with an outcome of interest (cases) with a group who do not have the outcome (controls). This study aims to looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group and with that to determine the relationship between that risk factor and the outcome.
So in this case, the cases are children with pervasive development disorder and the control is those without the disorders.
These studies are normally observational because no intervention is attempted.
Answer:
Lead is the major pollutants of high-tech gadgets, occupying 40%, while other metals 75%.This is because Pb forms lager components of these gadgets.For example a desktop computer contains about 10 pounds of Pb.
The lead to recycle these material to prevent pollution is important.
Explanation:
Answer: Nitrogen stays in the air.
Hope this helps! :D
-TanqR
(Please mark me as brainliest)
