I really don't understand this question

Question 9: (from chapter 13) Here is a data set on various measures of the 50 United States. The murder rate is per 100,000, HS graduation rate is in %, income is per capita income in dollars, illiteracy rate is per 1000, and life expectancy is in years. Find a regression model for life expectancy with three predictor variables by trying all four of the possible models. (Yes, you should run 4 different regression models, each time with four three out of the available 4 independent variables). a) Which model appears to do the best? b) Would you leave all three predictors in thismodel? c) Does this model mean that by changing the levels of the predictors in this equation, we could affect life expectancy in that state? Explain. b) Be sure to check the conditions for multiple regression. What do you conclude? State Name Murder HS Grad Income Illiteracy Life Exp Alabama 15.1 413 3624 2.1 69.05 Alaska 113 66.7 6315 1.5 6931 Arkzona 7.8 58.1 4530 70.55 Arkansas 10.1 39.9 3378 1.9 70.66 California 103 62.6 5114 1.1 71.71 Falarada ARRA Connecticut 3.1 56 5348 1.1 72.48 Thala wa ra Florida 10.7 52.6 4815 13 70.66 110 An K Angi 68 44 Howall 610 10 Trisha 41 10 71 87 Thank In 14 Indiana 7.1 52.9 4458 0.7 70.88 Inwa 71 71 56 40 0 71 48 Kanturby 1717 1 Tauklana 147 Maina n T Tn 10 Maryland 471 4700 In 71 Maccarhucatte 1 1 Michinam 11 1 Th 61 Minnesota ARTE 17 06 FR no Mkenurl 4764 Mantons 40 7 LFEF Nahracka 40 1 Nevada 11.5 65.2 $149 New Hampshire 303 57.6 4281 71.23 New Jersey 5.2 52 5 5237 1.1 70.93 New Mexico 9.7 55.2 3601 22 70.32 New York 10.9 52 7 1.4 TO.55 North Carolina 11.1 38 5 3875 69.21 North Dakota 1.4 50.3 7.4 53.2 4561 Oklahoma 64 51.6 3983 1.1 71.42 Oregon 42 72.13 Pennsylvania 6.1 50.2 4449 1 70.43 Rhode Island 2.4 46.4 4558 13 71.9 South Carolina 3635 23 67.96 South Dakota 1.7 53.3 4167 Tennessee 11 41.8 3821 1.7 TO.11 Tens 12 2 47.4 4185 70.9 Utah 4.5 673 4022 0.6 Vermont 5.5 57.1 3907 71.64 Virginia 9.5 47.8 4701 1.4 Was hingion 43 06 71.72 West Virginia 41.6 3617 1.4 69.45 Wheens in 54.5 4468 72.48 Wyoming 62.9 4566 0.6 TO.29