Why are all the people on earth members of the same biological sprecies?

Are all toddler boys hard to pottytrain?

Which of these is most likely to prevent pregnancy? a. tracking of female body temperature to identify ovulation times b. proper condom use c. male withdrawal before ejaculation d. proper spermicide use

Which statement best illustrates that problem solving can create new medical devices? robert hooke was in charge of verifying the information that was sent to the royal academy. william harvey did experiments with apes to learn about the circulatory system. the stethoscope was invented because the physician did not want to put his head on women's chests to listen to their heart and lungs. anton van leeuwenhoek was a very curious man and looked at just about everything under this microscope.