Which is the most effective action for people to take in order to reduce greenhouse gas emissions?

taking the bus more often
using a car powered by fuel cells
driving a car only five days a week
using a car that travels farther on each gallon of gas

The correct answer is using a car powered by fuel cells.

Explanation:

A fuel cell utilizes the chemical energy of hydrogen or another fuel to effectively and cleanly generate electricity. If hydrogen is used as fuel, then water, heat, and electricity are the only products formed. Thus, using a car powered by fuel cells would be the most efficient action for the individuals to take in order to minimize emissions of greenhouse gases.  

The fuel cells are specific in terms of the array of their potential uses, as they can offer power for the systems as big as a utility power station, and as small as a computer. The fuel cells have an application in various things, which comprises material handling, transportation, emergency back-up power applications, and others.  

they emit helium gas that attaches to nearby planets.

they remove low-mass elements from the planets’ crust.

they cause nuclear fusion inside the inner core of planets.

they produce heavy elements such as iron and gold.

explanation:

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.