The _____ is the inner layer of the embryo from which the lungs and digestive system develop.

Correct Answer: C

Rationale: The endoderm is the correct answer. It is the innermost layer of the embryo that gives rise to organs such as the lungs, digestive system, liver, and pancreas. The neural tube (Choice A) forms the brain and spinal cord, not the lungs or digestive system. Mesoderm (Choice B) develops into structures like muscles, bones, and circulatory system, not the lungs or digestive system. The umbilical cord (Choice D) serves as a connection between the embryo and the placenta, providing nutrients and oxygen, but it is not the layer from which lungs and digestive system develop.

Correct Answer: C

Rationale: Teratogens are environmental agents, such as drugs, chemicals, or infections, that can cause harm to a developing embryo or fetus. Mutations (Choice A) refer to changes in the DNA sequence and are not environmental agents. Autosomes (Choice B) are chromosomes that are not involved in determining an individual's sex and are not environmental agents that harm the embryo or fetus. Androgens (Choice D) are a group of hormones that are more related to male sexual development and function, not environmental agents that harm the embryo or fetus.

Correct Answer: B

Rationale: Syphilis is the correct answer. Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. If left untreated, it can progress through various stages and potentially attack major organ systems, causing severe complications. Rubella, Cystic fibrosis, and Phenylketonuria are not sexually transmitted infections. Rubella is a viral infection, Cystic fibrosis is a genetic disorder affecting the lungs and digestive system, and Phenylketonuria is a genetic metabolic disorder. These conditions do not typically affect major organ systems in the same way as untreated syphilis.

Correct Answer: B

Rationale: Mitosis is the correct answer because it is the process of cell division in which a cell duplicates its DNA and divides into two identical daughter cells. During mitosis, the DNA is replicated, and each daughter cell receives an identical copy of the genetic material. Amniocentesis is a medical procedure to collect amniotic fluid for prenatal genetic testing and is not related to DNA duplication. Meiosis is a type of cell division that produces gametes with half the genetic material of the parent cell, leading to genetic diversity. Mutation is a permanent alteration in the DNA sequence that can lead to genetic variations but is not the process of DNA duplication.

Correct Answer: C

Rationale: The correct answer is C: uterus. The uterus is the organ where the embryo implants and the fetus develops during pregnancy. The placenta (choice A) is an organ that develops during pregnancy and provides nutrients and oxygen to the fetus, but it is not the organ where the embryo and fetus physically develop. The ovum (choice B) is the female reproductive cell or egg that is fertilized by the sperm to form an embryo, but it is not the organ where the embryo and fetus develop. The amniotic sac (choice D) is a membrane filled with amniotic fluid that surrounds and protects the fetus, but it is not the organ where the embryo and fetus physically develop.