Answer:
hertz
Explanation:
Usually frequency is measured in the hertz unit, named in honor of the 19th-century German physicist Heinrich Rudolf Hertz. The hertz measurement, abbreviated Hz, is the number of waves that pass by per second. For example, an "A" note on a violin string vibrates at about 440 Hz (440 vibrations per second).
Researchers are someone who searches about someone and learns about someone's daily lives or talents.
Answer:
D
Explanation:
"Jeff, the famous author and inventor, arrived late at the lecture hall for his public appearance."
The famous author and inventor is adding details on Jeff, so commas have to surround it.
Answer:
Robert Martinson
Explanation:
After writing about his experiences in prisons, where he carried on research, American sociologist Robert Martinson claimed that rehabilitation programs did not work for convicted criminals who reoffended repeatedly. As a result, even though he later changed his mind, his findings were disputed at the time and caused the cancellation of several rehabilitation programs in the US.
