Oxygen (o) is a gas found in the 16th column of the periodic table. what statement is true about oxygen and the other elements in that column?

Oxygen is the most abundant element in erath's crust (46 % by weight). Oxygen is present in Group 16 in the periodic table. The other elements in this period are: Sulphur (S), Selenium (Se), Tellurium (Te). The general electronic configuration of the elements present in Group 16 is: ns² np⁴. Oxygen is smallest in size among other elements in the same group. It exists as O₂ molecule where O=O bond is found. These O₂ molecules are associated through  van der Waal's force of attraction which are very weak, because of that O₂ exists as gas. Except oxygen, other elements do not form divalent molecule and they have  d-orbitals, so they can show catenation property by which large number of atoms are connected via covalent bonds. Hence those elements are not gaseous. Sulphur, Selenium and Tellurium are solid,

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.