How do scientists know that the human activity is the major force behind climate change?

It is because of Various things that we do, If we did not exist, several animals that went extinct because of us, would have thrived, If it wasn't for us filling the sky with so much CO2's, we wouldn't have the Earth heating up even more. Also, other things that we do such as Urbanization, Desertification, and Deforestation. All of these words will be defined under this text.

Explanation:

Deforestation: When humans cut down too many trees can result in habitat loss/ more CO2's

Desertification: When land used to be a grassland but humans used too much of a resource and turned it into a hot, sandy wasteland.

Urbanization: When you take land and fill it with tons of buildings, homes, and businesses. This can result in over-crowding, and spreading of diseases.

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.

i believe the answer is a.