Jory is trying to identify a sample of an unknown mineral. His teacher tells him that it is one of the minerals listed in the table below. Mineral Hardness
(Mohs scale) Shape Density
(g/cm3) Color Luster Streak Cleavage Fracture
Graphite 1 lamellar veins to earthy masses 2.09-2.23 steel gray metallic black Yes Yes-flaky
Talc 1 flattened or tabular 2.7-2.8 white to green non-metallic white Yes-basal Yes-uneven
Gypsum 2 tabular, bladed or blocky 2.3 white to colorless to gray non-metallic white Yes Yes-uneven
Hematite 6 tabular 5.3 steel gray metallic reddish-brown No Yes-uneven
Pyrite 6 cube, octahedron and pyritohedron 5.00-5.02 golden yellow metallic greenish black No Yes-conchoidal
Quartz 7 two rhombohedrons 2.6-2.65 colorless to several other shades non-metallic white Yes-weak rhombohedral Yes-conchoidal

He measures the mineral's hardness and finds that it is a 6 on the Mohs scale. What could he do next to determine which mineral it is?
A.
identify its luster
B.
measure its density
C.
test its cleavage
D.
measure its volume

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.