Asequence of thermonuclear fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon, oxygen, etc., into heavier nuclei and also generate excess energy up to a limit beyond which no further energy-producing reactions can occur. the element that is produced when this limit is reached is
select one:
a. oxygen.
b. iron.
c. uranium.
d. silicon.

B. iron.

Explanation:

The strong force holds not only the protons together, but also them with the neutrons (among which there is actually no attraction or repulsion given the lack of electric charge of the neutron), so that it can be said that this force is the responsible for the atomic nuclei remain armed. Electrons and neutrinos are not influenced by this force, the first because they move great distances from each other. The radius of action of the strong force is very small, just enough to fulfill its cohesive function. This force is the source of the great energy that is generated in the nuclei of the stars, such as our sun, which function as fusion reactors, that is, where certain elements are successively composed in long periods from the lightest, the hydrogen (H) that mostly constitutes the stars, towards others of greater complexity, that is to say of greater atomic weight, until reaching the iron (Fe). This process is the opposite of what happens in fission reactions, which are those that occur in the reactors of nuclear power plants, where elements of great atomic weight, such as uranium (almost 240 times heavier than hydrogen), they decompose emitting a quantity of particles from their nucleus and thus forming atoms of simpler elements, that is to say with smaller nuclei, with an enormous emission of energy.

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 answer to your question is c