What feature distinguishes male embryo from female at eight weeks of age?
a. males have a y chromosome
b. males have well developed primary reproductive organs
c. male testes have descended into the scrotum
d. in males, the ovaries have degenerated
e. all of the above

A, B & D

Explanation:

It is not possible to distinguish the sex of a fetus below seven (7)weeks. At this stage only observation of chromosomes through karyotype can determine the sex.  The male fetus will have an XY sex chromosome pair while females will have an XX chromosome pair. After the eighth weeks internal and external genitalia begins to differentiate. The testes and ovaries (the primary reproductive organs) begin to develop in males and females respectively. In males the paramesonephric ducts regresses while the mesonephric ducts begin to develop into testes. In females the mesonephric ducts regresses while the paramesonephric ducts begin to develop into ovaries.

the correct answer is b

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.