The 15th amendment, ratified in 1870, did not secure the right of african americans to vote primarily because a. it did not state that voting rights could not be denied to african americans. b. the federal government did not intervene to uphold the amendment. c. it was repealed by congress shortly after ratification. d. it prevented state leaders from acting on behalf of potential voters who were being discriminated against.

Running and sleep. sufficient sleep is important for adolescents for both their neural and psychological development. despite this, daytıme sleepiness and poor physical and psychological functioning related to chronic sleep disturbances are common. there is a growing body of evidence that exercise is associated with both better sleep and improved psychological functioning sixty participants were recruited from a high school in northwesten switzerlandthey were randomly assigned to either a running group or a control group, 30 to each group the running group ran every moming for a little over 30 minutes on weekdays for a three-week period. all participants used a sleep log for subjective evaluation of sleep, and sleep was also objectively assessed at the beginning and end of the study using a sleep electroencephalographic device that measured quantities such as sleep efficiency and time spent in the four different sleep phases. running was found to have a positive impact on both objective and subjective measures of sleep functioning what are the explanatory variable(s) and the response variable(s)? (a) outline the design of the experiment (b) (c) here are some more details on the treatment and control groups. all participants arrived at school at 7 a.m., and the running group did two laps on the track and then ran cross countrv in groups of at least four people for 30 minutes the control group remained seated at the track, worked on horpework. and interacted with each other. when the runners returned, all participants prepared for school and ate a breaktast that was provided. iwhy do you think the experimenters had the control group arrive at 7 am interact withdassmates and have breaktast together? explain. do you think having the control eroup do these activities is important for the types of conclusion that can be reached? how?

Which choice best describes the general trend for the countries shown, for the period 2008 - 2010?

Should the city pass a ban on skateboarders on all public property, or are the citizens who oppose the ban right when they argue that there are benefits to having the skateboarders in public parks? plan and write a response in which you state your position and persuade readers to agree with you. support your position with reasons and examples drawn from the proposed amendment to ban skateboarding and from information in the letters to the editor, as well as from your own experience.