A(n) uses lines to indicate pairs of shared electrons in a molecule.

a. anode
b. covalent bond
c. crystal
d. family
e. hydrocarbon
f. ionization energy
g. ion
h. ionic bond
i. metal
j. metalloid
k. molecular formula
l. nonmetal
m. period
n. polar molecule
o. polymer
p. single bond
q. structural formula
r. superconductor

This question is a little confusing. Good questions should not be confusing. Good questions should let the student have clarity on what is being asked and which opiton is undoubtely the right answer.

Let me tell you why I say this.

A line (-) is used to represent pairs of share electrons and that is a covalent bond.

So the line is used when you have covalent bonds. Is that the answer? It should be but when study the other options you find another option which is a good fit.

A line is used in the structural formula to represent the covalent bonds, i.e. the pairs of shared electrons.

So, the line is used to represent  covalent bonds (option b) in a structural formula (option q)

This is an example:

      H
       |
H - C - H
       |
      H

That is the structural formula of CH4 and the lines represent the covalent bonds (pairs of shared electrons).

If you have to pick one, it sounds better the option q. (only because syntaxis), i.e.

A structural formula uses lines to indicate pairs of shared electrons in a molecule.

Because it is not exact that the covalent bonds uses lines ... but that lines are used to represent covalent bonds.

Conclusion: the option q.

 

Answer: abeexplanation:

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.

C, small, hard spheres with insignificant volumes