How to distinguish between metals and non-metals

Explanation:

Metals tend to have 1-3 valence electrons in their outer shell, while non metals have 4-8 electrons in their outer shell. Metals are natural elements that are hard, opaque, shiny and dense. While non metals are chemical substances that are soft, transparent, non-shiny and brittle. You can also distinguish a metal from a non-metal based on its appearance: metals are Lustrous while non metals are Non-lustrous. In other words metals are shiny while non metals are usually dull or simply "not shiny". Melting and Boiling point can also help distinguish between metals and non metals: metals tend to have : very high melting and boiling point. Nonmetals have Low melting and boiling point. Metals are also good conductors of heat and electricity, while nonmetals are poor conductor of heat and electricity. And lastly, metals are malleable and are always hard except for sodium, and nonmetals are non-malleable and are soft except for diamonds.

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.