Why is it desirable that microscope objectives be parfocal

How has the immigration of the 1990s affected the social and economic life of the united states?

What is meant by a symmetrical unimodal distribution? a. a distribution is the frequency at which a certain value of a variable is obtained during a study. a symmetric unimodal distribution is a distribution where there is one value with a larger frequency than any other and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other. b. a distribution is a pattern of frequencies for the various values of a variable collected in a study. a symmetric unimodal distribution is a distribution where there is one value with a larger frequency than any other and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other. c. a distribution is the frequency at which a certain value of a variable is obtained during a study. a symmetric unimodal distribution is a distribution where there is a uniform frequency, meaning the frequency of every value is same, and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other.

Which of the following is not among the root causes of poverty in the united states? size of family disabilities advanced degrees underemployment