Which is true about each element in a period or horizontal row of the periodic table? a. each element has one more outer shell than the element before it. b. each element has one more outer electron than the element before it. c. each element has one more isotope than the element before it. d. each element bonds with the element before it.

The  true  about element in  period or  horizontal  row  of periodic table is

Each  element  has one more outer electron than the element before it. (answer B)

 Explanation

 In periodic table  there are four horizontal rows(periods) that is  period 1,2,3 and 4.

Across the period each element has one more electron than element before it.

For example  Na and Mg which  are in  periodic 3.

Na  has 2.8.1  or [Ne] 3s¹ electron configuration  while Mg has  2.8.2  or [Ne] 3S² electron configuration.

Since Mg has 2   outer electrons  while Na has 1 outer electron, Mg has more electron than Na.

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.

they vary. it used to be meat, grain, bread, candy, beverages, donuts, and fruits/vegetables. now they added exercise in.