Which one of the following is caused by a bacterial pathogen?
- A.AIDS
- B.Dengue fever
- C.COVID-19
- D.Typhoid fever
Correct answer
Explanation
The correct answer is D, Typhoid fever. Typhoid is caused by the bacterium Salmonella typhi; the other three are viral diseases.
Salmonella typhi spreads through food and water contaminated with the faeces of an infected person, which is why typhoid is common where sanitation is poor. The bacteria enter the small intestine and then the blood, causing a long, high fever, weakness, stomach pain and, in severe cases, perforation of the intestine. It is confirmed by the Widal test and treated with antibiotics, and vaccines are available. Clean water and hand washing are the main means of prevention.
A is wrong because AIDS is caused by the human immunodeficiency virus (HIV), which attacks helper T-cells.
B is wrong because dengue is caused by the dengue virus, carried by the Aedes aegypti mosquito.
C is wrong because COVID-19 is caused by the coronavirus SARS-CoV-2.
Exam tip: typhoid = Salmonella typhi, Widal test; other bacterial diseases include cholera, tuberculosis, tetanus and diphtheria.
Practice Questions
View allWhich one of the following can charge an insulator?
- A.Current electricity
- B.Static electricity
- C.Magnetic field
- D.Gravitational field
Show answer
An insulator is charged by friction: rubbing transfers electrons from one surface to another, and because electrons cannot move through an insulator, the charge stays where it is as static electricity.
Read the full explanation →A glass prism splits white light into different colours. This phenomenon is called dispersion of light by prism. Which one of the following statements is correct?
- A.Red light will deviate the most and it is because of the reflection of light.
- B.Violet light will deviate the most and it is because of the refraction of light.
- C.Red light will deviate the most and it is because of the refraction of light.
- D.Violet light will deviate the most and it is because of the reflection of light.
Show answer
In glass, violet light has the shortest wavelength and the highest refractive index, so it bends the most; dispersion is a result of refraction.
Read the full explanation →A 5 N force is defined when a mass of 10 kg is accelerated with
- A.5.0 cm/s²
- B.0.5 m/s²
- C.0.5 cm/s²
- D.5.0 m/s²
Show answer
By Newton's second law, F = m × a, so a = F ÷ m = 5 N ÷ 10 kg = 0.5 m/s².
Read the full explanation →The breakdown of glucose in cytoplasm results in the formation of
- A.pyruvate and energy
- B.pyruvate and carbon dioxide
- C.pyruvate and oxygen
- D.pyruvate and nitrogen
Show answer
In the cytoplasm, glucose is split by glycolysis into two molecules of pyruvate, releasing a small amount of energy as ATP.
Read the full explanation →Which one of the following is the correct sequence in increasing complexity?
- A.Protein - Organism - Tissue - Organ
- B.Protein - Organ - Tissue - Organism
- C.Protein - Organism - Organ - Tissue
- D.Protein - Tissue - Organ - Organism
Show answer
Living things are built up level by level: molecules such as proteins form cells, cells form tissues, tissues form organs, organs form organ systems, and these together make an organism.
Read the full explanation →