Which type of variable is kept unchanged throughout the experiment so as not to influence the experiments outcome? independent dependent control

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Mr. polanski likes the cost of an hmo plan available in his area, but would like to be able to visit one or two doctors who aren't participating providers. he wants to know if the point of service (pos) option available with some hmos will be of any in this situation. what should you tell him? mr. polanski likes the cost of an hmo plan available in his area, but would like to be able to visit one or two doctors who aren't participating providers. he wants to know if the point of service (pos) option available with some hmos will be of any in this situation. what should you tell him?

Compare and contrast the environmental consequences of reliance on coal with reliance on petroleum.