A template of a Venn diagram representing common and differentiating characteristics of covalent and ionic bonds is shown. Two overlapping circles are shown. On top of the left-hand circle Ionic Bond is written and on top of the right-hand circle Covalent bond is written. The non-overlapping space on the left is marked A, the overlapping space is marked B and the non-overlapping space on the right is marked C.

Which of the following characteristics can be written only in space B?

Occurs in substances that have at least one non-metal
Occurs in substances that have a repeating lattice structure
Occurs in substances that have discrete molecular structure
Occurs in substances that have high melting points

Occurs in substances that have at least one non-metal

Explanation:

The intersection point which is space B is the place where both ionic and covalent bonds shares the same properties.

An ionic bond is formed by the transfer of electrons from a metal to receiving non - metal.

A covalent bond is formed by the sharing of electrons between non - metals.

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.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.