this excerpt is from the U. S. Supreme Court decision in Brown v. Board of Education of Topeka, Kansas (1954). in the excerpt from the Court's ruling, what does the word "instrument" mean?

the boundarys like convergent divergent and transform it causes subduction

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.

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.