Which statement best identifies the characteristics of language development in a toddler?

Correct Answer: B

Rationale: The correct answer is B because toddlers typically understand more words and concepts than they can express verbally due to their limited vocabulary and developing language skills. This is supported by research in child development showing that receptive language skills (understanding language) usually precede expressive language skills (speaking). Toddlers may struggle to articulate their thoughts and feelings, leading to frustration. Now, let's evaluate the other choices: A: Language development skills actually accelerate during the toddler period, not slow down. C: While toddlers may have pronunciation issues, most of their speech is usually understood by caregivers. D: A toddler's vocabulary usually ranges from 200 to 500 words, not strictly 600 words.

Correct Answer: A

Rationale: Aortic stenosis is the correct answer as it is a defect that causes narrowing of the aortic valve, leading to obstruction of blood flow from the left ventricle to the aorta. This obstruction increases the workload on the heart and can result in symptoms such as chest pain and heart failure. Tricuspid atresia, atrial septal defect, and transposition of the great arteries do not directly cause obstruction to blood flow in the same way as aortic stenosis. Tricuspid atresia involves the absence of the tricuspid valve, atrial septal defect is a hole in the atrial septum, and transposition of the great arteries involves a switch in the positions of the pulmonary artery and aorta.

Correct Answer: A

Rationale: The correct answer is A: Susceptibility to respiratory infection. Children with congenital heart disease often have compromised immune systems due to their cardiac condition, making them more prone to respiratory infections. This is because the heart defect can affect blood flow to the lungs, leading to decreased oxygen levels and weakened lung function. As a result, these children are at higher risk for respiratory complications. Incorrect choices: B: Bleeding tendencies - While some heart conditions may lead to clotting issues, bleeding tendencies are not a frequent complication of congenital heart disease. C: Frequent vomiting and diarrhea - These symptoms are not typically associated with congenital heart disease, unless there are specific underlying conditions causing them. D: Seizure disorder - Seizures are not a common complication of congenital heart disease; they are more often related to neurological issues or other medical conditions.

Correct Answer: D

Rationale: The correct answer is D: leukocytes. Leukocytes are a general term encompassing all white blood cells, which play a crucial role in the immune system. They are responsible for defending the body against infections and foreign invaders. Hematopoietic cells (A) refer to the cells that give rise to all blood cells, including red and white blood cells. Myeloid progenitors (B) are specific progenitor cells that give rise to certain types of white blood cells, red blood cells, and platelets. Dendritic cells (C) are a specific type of white blood cell that plays a key role in the immune response by presenting antigens to other immune cells. Overall, leukocytes are the most appropriate term to describe all white blood cells due to their broad and inclusive nature in the immune system.

Correct Answer: D

Rationale: The correct answer is D because helper T cells do not directly kill pathogen-infected cells. Helper T cells assist in coordinating the immune response by activating other immune cells. T-cell activation involves cell division and differentiation (Choice A), effector B cells differentiate into plasma cells to secrete antibodies (Choice B), and plasma cells are responsible for antibody secretion (Choice C). Therefore, the mismatched pair is helper T cell: kills pathogen-infected cells.