Answer:
D) Testing has shown that teenage boys between the ages of 15-18 sleep longer than teenage girls in the same age group.
Explanation:
The best way to revise this sentence is given in option D.
Option A lacks all necessary details, simply stating that males sleep longer than females. The research/testing, children's age, and the hours are not mentioned.
Option B feels like the second best, but a very important piece of information is missing - the specific age. Teenagers are children aged 13-19, and the difference between 13- and 19-year-olds is huge.
Option C also lacks information about the subjects' age.
Option D is also not ideal but feels the most complete. It doesn't mention how much longer exactly the boys sleep, but that detail isn't as important as the specific age is.
The difference between the split ring commutator in a DC motor and the slips rings in an AC generator can be tricky. The split ring makes changes in the rotation every so often. A slip ring just stays in place and is only used as a connector. So a slip ring is for DC, whereas the split ring is used for AC.
