Some research examining the facial feedback hypothesis has found that subliminal exposure to faces displaying a specific emotion is associated with changes in the observer's facial muscles that correspond to that displayed emotion. these findings have not been consistently repeated, however. this makes it harder to know if subliminal emotional perception is or is not real due to the concept of

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.