Correct Answer: D

Rationale: The correct answer is D (69%). The UN projects that by 2050, around 69% of the world's population will live in urban areas. This is based on current global urbanization trends and population growth rates. Urban areas are experiencing rapid population growth due to factors like rural-to-urban migration and natural population increase. Choices A, B, and C are incorrect because they underestimate the expected urban population growth by 2050. A (35%), B (56%), and C (60%) are too low compared to the projected 69%. Urbanization is a significant global trend, and it is essential to consider the implications of this shift for sustainability, infrastructure development, and resource allocation.

Correct Answer: A

Rationale: The correct answer is A: Helicobacter. Helicobacter pylori is the main causative agent of peptic ulcer disease and is characterized by its gram-negative arcuate bent shape and positive urease activity. Helicobacter pylori specifically colonizes the stomach mucosa and is associated with various gastrointestinal disorders. Spirochetes (choice B), spirilla (choice C), and Leptospira (choice D) are not typically associated with peptic ulcer disease or stomach mucosa infections, making them incorrect choices in this context.

Correct Answer: A

Rationale: The correct answer is A because growth factors are essential nutrients that bacteria cannot synthesize on their own and must obtain from the environment for their growth. Bacteria rely on these external factors for processes like cell division, metabolism, and survival. Choice B is incorrect because bacteria can only synthesize growth factors in limited amounts, not sufficient for their growth. Choice C is incorrect as bacterial cells do not store growth factors in granules. Choice D is incorrect because bacterial cells do not synthesize growth factors in large amounts.

Correct Answer: D

Rationale: The correct answer is D: Multiplies by binary fission. Bacterial cells reproduce through binary fission, where a single cell divides into two identical daughter cells. This process is essential for bacterial growth and multiplication. A: The oxidative phosphorylation does not take place in the mitochondria of bacterial cells but in the cell membrane. B: Capsules are not organelles but outer protective layers found in some bacterial cells. C: Bacterial cells contain both DNA and RNA, essential for their genetic information and protein synthesis.

Correct Answer: A

Rationale: The correct answer is A: Antibiotic. Brucellosis is a bacterial infection, and antibiotics are the primary treatment to target and eliminate the bacteria causing the disease. Antibiotics such as doxycycline and rifampin are commonly used for brucellosis treatment. Donor immunoglobulin (B) is not used to treat brucellosis as it is not caused by a deficiency in antibodies. Inactivated therapeutic vaccine (C) is used for prevention, not for treating active infections. Antitoxic serum (D) is used to neutralize toxins produced by bacteria, not to directly kill the bacteria themselves in cases like brucellosis.