Why are some solutes soluble in water and others in cyclohexane

The answer to the question is due to the ability of the solute to form interaction with the solvent. Some solutes (hydrophylic) are able to form bonds with water molecules and so dissolve, while others which are not able to dissolve in water (hydrophobic) are able to form bonds in non polar solvents such as cyclohexane

Explanation:

A solution is formed by the interaction of the solute particles with the solvent such that the particles of the solute freely diffuse through out the solvent.

However, some solute are hydrophilic (easily attracted to water) while others are hydrophobic (repels water). The hydrophilic solute is a polar solute that has an NH or OH bond  and easily forms hydrogen bonds with water molecules. The hydrophobic solute, which may be polar, consist of mainly CH bonds which do not dissolve well in water but dissolve in solvents such as benzene and cyclohexane with which they form interactions including Van Der Waals forces.

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.

2b2t

explanation:

2b2t