Which of the following is *true* of the placenta? Question 18 options: 1) It fully develops six months after birth. 2) It forms during the seventh month of prenatal development. 3) It is the fluid-filled sac that houses the developing embryo and fetus. 4) It allows the exchange of nutrients between the embryo and the mother, while at the same time filtering out harmful material.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.