Question 1150479
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ANSWER A.<br>
The difference between a brother and sister is 5.31 times x3; x3 is 1 for a male and 0 for a female.  So the expected difference between the heights of a brother and sister is 5.31*(1-0) = 5.31.<br>
Since A is the answer, presumably choices B to E are all incorrect.<br>
x1 relates to the mother's height and x2 to the father's height; that means answer choice C  can't be right.<br>
And for answer choices B, D, and E, the coefficients in the equation don't match with the information given in the answer choices.<br>