Final answer:
By the eighth week of development, it is true that an embryo exhibits detectable brain activity, with major brain structures in place and initial functioning of the kidneys, as part of various complex developmental processes.
Step-by-step explanation:
It is true that by the eighth week of development, an embryo exhibits detectable brain activity. Between the fifth and eighth weeks of embryonic development, a sequence of rapid changes occurs. During the sixth week, the embryo begins to experience uncontrolled limb movements and the gastrointestinal system's rapid growth causes the intestines to loop into the umbilical cord.
By the seventh week, the facial structure becomes more complex, including the development of nostrils, outer ears, and eye lenses. By the eighth week, the head is almost as large as the body, major brain structures are established, and bone begins to replace cartilage through ossification. Additionally, the kidneys start functioning, and the amniotic fluid ingested by the fetus can be excreted as urine.