[Solved] Ultrasound and maternal serum marker tests are less informative than amniocentesis or chorionic villus sampling (CVS) in diagnosing trisomy 21 because A) ultrasound and maternal serum markers check chromosomes, and CVS and amniocentesis do not. B) ultrasound and maternal serum markers do not check chromosomes, and CVS and amniocentesis do. C) maternal serum markers and amniocentesis check chromosomes, and ultrasound and CVS do not. D) ultrasound and CVS check chromosomes, and maternal serum markers and amniocentesis do not. Successful Long-Term Relationships: Relationships that are thriving and enduring, marked by mutual understanding, respect, and love. Paternity Uncertainty: The impossibility for a male to be absolutely certain that he is the biological father of a child, due to the nature of internal fertilization and gestation in females. Extradyadic Sex: Sexual activity that occurs outside of a committed relationship, often considered a breach of exclusivity. Erotic Plasticity: The degree to which an individual's sex drive and sexual interests can change based on various social, environmental, and situational factors.