Correct Answer: B

Rationale: Rationale: - Proteins are made up of long chains of amino acids. - Amino acids are the building blocks of proteins and are considered monomers. - Monomers are the individual units that can be linked together to form larger molecules called polymers. - In the context of proteins, amino acids are the monomers that are linked together through peptide bonds to form polypeptide chains, which then fold into functional proteins. - Residues refer to the specific amino acids within a protein after certain modifications or cleavages have occurred, so it is not the correct term for the building blocks of proteins. - Macromolecules are large molecules made up of smaller subunits, such as proteins, nucleic acids, and carbohydrates, but they are not the specific building blocks of proteins. - Peptides are short chains of amino acids linked by peptide bonds, but they are not the fundamental building blocks of proteins.

Correct Answer: A

Rationale: Pure substances have a definite and constant composition, meaning they are made up of only one type of atom or molecule with fixed proportions. This composition does not vary. On the other hand, mixtures are composed of two or more substances physically combined. The components of a mixture can be present in varying proportions, leading to a variable composition. Choice A is correct as it accurately distinguishes between pure substances and mixtures based on the fixed composition of pure substances and the variable composition of mixtures. Choice B is incorrect because mixtures, not pure substances, have variable compositions. Choice C is incorrect as both pure substances and mixtures can exist in different states. Choice D is incorrect because pure substances can be compounds as well, not exclusively elements, and mixtures can contain elements and compounds.

Correct Answer: C

Rationale: Disinfecting and reusing sterile medical devices is not a recommended method for preventing healthcare-associated infections (HAIs). Reusing sterile medical devices can increase the risk of infections due to inadequate sterilization or potential damage to the devices during the reprocessing process. Proper sterilization and disposal of single-use medical devices are essential in preventing the transmission of infections in healthcare settings. A) Handwashing with soap and water is a crucial method for preventing HAIs as it helps to remove and reduce the number of pathogens on the hands of healthcare workers, preventing the spread of infections. B) Proper use of personal protective equipment (PPE) such as gloves, gowns, masks, and eye protection is important in preventing the transmission of infections between patients and healthcare workers. C) Disinfecting and reusing sterile medical devices is not a recommended practice as it can lead to the transmission of infections if the devices are not adequately sterilized. Using single-use sterile medical devices helps to ensure that each patient receives a sterile device, reducing the risk of infections.

Correct Answer: C

Rationale: Regularly engaging in moderate exercise benefits the lymphatic system by promoting circulation and aiding in the removal of toxins and waste products from the body. This helps maintain a healthy lymphatic system. Consuming a high-sugar diet can lead to inflammation and hinder lymphatic function. Maintaining a sedentary lifestyle can result in poor circulation, which negatively affects the lymphatic system. Smoking cigarettes introduces toxins into the body, further burdening the lymphatic system. Therefore, the correct lifestyle practice that can benefit the lymphatic system is regularly engaging in moderate exercise.

Correct Answer: C

Rationale: Antibodies are proteins produced by specialized white blood cells called B lymphocytes (B cells). These B cells mature in the bone marrow, where they undergo a process of differentiation and maturation to become plasma cells that secrete antibodies. The bone marrow is the primary site for the production of B cells and antibodies in the immune system. The thymus gland is responsible for the maturation of T lymphocytes (T cells), not antibody production. The spleen and lymph nodes play roles in filtering and trapping pathogens but are not the main organs responsible for producing antibodies.