Select the correct answer from each drop-down menu. Complete these descriptions of different kinds of chemical reactions.

A
reaction involves burning. This reaction requires energy to start, but it releases more energy than is required to start it. Oxygen is always a reactant, and the products are usually carbon dioxide and water.

A
reaction occurs when a compound breaks down. This reaction has one reactant and two or more products. Energy, as from a battery, is usually needed to break the compound apart.

A ___
reaction occurs when two substances combine to form one substance. An example of this kind of reaction is rusting, in which iron reacts with oxygen.

A reaction that involves the replacement of atoms is a
reaction. An atom from one reactant replaces an atom in the other reactant. This kind of reaction has two reactants and two products. An example is the neutralization of an acid and an alkali.

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.