Which is a characteristic of nuclear fusion but not nuclear fission?
a. releases large amounts of energy
b. is the energy source of stars
c. is used in electric power plants
d. requires little energy to occur

 Nuclear fusion is the energy source of stars.

This is the option thats characterisitic of nuclear fusion and not nuclear fission.

Explanation:

Both nuclear fusion and nuclear fission releases large amount of energy.

Nuclear fission is a process of splitting a large radioactive nuclei into lighter nuclie and the energy released is used to generate electricity.

Nuclear fission requires little energy to occur.

Nuclear fusion is the process when two lighter nuclei under high Temperature and pressure combine to form a heavier nuclei to release large amount of energy.

And this process generally happens only in stars.

Nuclear fusion is the energy source of stars.

Nuclear fusion cannot be done on earth as earth cannot make this high Temperature and pressure,hence it cannot be used to generate electricity.  

Hence,nuclear fusion is the energy source of stars is the only characterisitic of nuclear fusion among these four options given here.  

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.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.