Scottish researchers compared rates of depression between 94 undergraduates who regularly kept diaries and 41 students who did not. they found that people who kept diaries were more likely to have depression than those who did not. the researchers said, "we expected diary-keepers to have some benefit, or be the same, but they were the worst off. you are probably much better off if you don't write anything at all."

Another explanation could be that people who are depressed are more likely to keep a diary. This is an observational study, so it is not possible to associate that writing in a diary as a cause, leads to depression as the effect.Their interpretation of the results was flawed because the researchers assumed an order of cause and effect and looked at the results only from one direction. Another example would be if we assume that obesity is related to depression. We can look at it two ways: that depression can lead to obeisty through over eating or the other way around, that overweight people are more likely to become depressed.

two jet streams that directly affect the formation of weather in the continental part are a polar jet and a subtropical jet. they are responsible for the transportation of weather systems, which directly affect people. the polar front is the boundary between cold air from the north pole and warmer equatorial air. both the polar jet and the subtropical jet blow from the west to the east, and follow the boundary between cold and warm air.

the strongest jet streams are polar jets, while subtropical jets are somewhat weaker.

the right answer is c. the polar jet stream is generaly stronger than the subtropical jet stream.