How many grams of carbon dioxide are produced when 16.0 g of methane and 48.0 g of oxygen gas combust?
Molar mass of CH4 = 16.0 g/mol
Molar mass of O2 = 32.0 g/mol
Molar mass of CO2 = 44.0 g/mol

Mass of CO₂ = 33 g

Complete combustion of Hydrocarbons with Oxygen will be obtained by CO₂ and H₂O compounds.  

If O₂ is insufficient there will be incomplete combustion produced by CO and H and O  

Reaction

CH₄ + 2O₂⇒CO₂ + 2H₂O

mol CH₄ :

mol O₂ :

A method that can be used to find limiting reactants is to divide the number of moles of known substances by their respective coefficients

Because O₂ ratio smaller then O₂ becomes the limiting  reactants

So mol CO₂ from limiting reactants

mol CO₂ :

mass CO₂ :

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.