What happens in this reaction and why? 3-methylbutane-1,3-diol + cro3 -->

Here we have to explain and get the product of the reaction between 3-methyl-1,3-diol and chromium-tri-oxide (CrO₃)

The reaction between 3-methyl-1,3-diol with chromium-tri-oxide (CrO₃) form 3-methyl-3-hydroxybutanal.

The CrO₃ is used as a mild oxidant to the alcohol. It only produces aldehyde or ketone depending upon the position of the -OH group in a secondary or primary alcohol.

Here we can see there are two hydroxy (-OH) group in the reactant. However one of the hydroxy is at terminal carbon atom, thus primary alcohol and other in between as tertiary alcohol.

As the reagent CrO₃ does not reacts on the tertiary -OH group thus the -OH group present at 3 position will not be oxidized. Thus only the terminal hydroxy group will oxidize to form the corresponding aldehyde.

Henceforth the final product of the reaction is 3-methyl-3-hydroxybutanal as shown in the figure.  

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.