The freshmen competed with the sophomores to see who could raise the most money by recycling. The appropriate design for testing the significance of the difference between the means is

Independent-samples t-test.

Step-by-step explanation:

We are looking for the appropriate design for testing the significance of the difference between the means.

Now, there is a parametric test known as the Independent Samples t Test and what this test does is that it compares the mean of two independent groups in order to find out whether there is statistical evidence that the related population mean is significantly different.

Thus, the test to be used here is Independent-samples t-test.

3. parallelogram

step-by-step explanation:

we turn each of our sides into direction vectors

ab=b-a=(3 - 7, 1 - 0) = (-4, 1)

bc=c-b=(1,6)

cd=d-c=(4,-1)

da=a-d=(-1,-6)

we see how the opposite sides have negated direction vectors; this is characteristic of a parallelogram.   we have congruent sides ab=cd and bc=da with unequal lengths because 1^2+6^2 is different from (-4)^2+1^2.   so it's not a square or a rhombus.  

we check the dot product of direction vectors of adjacent sides.   we have

ab dot bc = -4(1) + 1(6) = 2

that's not zero so the sides are not perpendicular.   we've ruled out rectangle.

the direction vectors indicate two pairs of congruent parallel sides, so we choose parallelogram over trapezoid.