Correct Answer: C

Rationale: The term 'etiology' refers to the cause or origins of a disease. In this context, the question is asking for the underlying reason or cause of the flu epidemic of 1918. Therefore, the correct answer is C. 'Etiology.' Choice A, 'Pathology,' is incorrect as it refers to the study of diseases rather than the cause itself. Choice B, 'Transmission,' is incorrect as it relates to how a disease spreads rather than its cause. Choice D, 'Mortality rate,' is incorrect as it refers to the number of deaths caused by a disease rather than the cause of the disease itself.

Correct Answer: B

Rationale: Depth refers to the distance or downward measurement from a surface. It is not the thickness of an object (Choice A), as thickness is the measure of how thick or thin an object is, not necessarily related to depth. Additionally, it is not the length of a surface (Choice C) because length typically refers to the longest dimension of an object rather than its depth. Finally, it is not the area between two points (Choice D) because area is a measure of the space within a boundary defined by points, while depth specifically refers to the vertical distance below a surface.

Correct Answer: B

Rationale: The correct answer is B: 'A sum total of many things.' Aggregate refers to the total or sum of different elements or components. Choice A, 'A part of the whole,' is incorrect as aggregate does not refer to just a part but the whole combined. Choice C, 'A small fraction,' is incorrect as aggregate denotes a larger amount, not a small fraction. Choice D, 'A gradual reduction,' is incorrect as aggregate does not imply reduction but rather accumulation or combination.

Correct Answer: B

Rationale: The correct answer is 'She has completed the project.' The sentence uses the present perfect tense with 'has completed,' which is the correct form of the verb. Choice A is incorrect due to the subject-verb agreement error ('She' requires 'has' instead of 'have'). Choice C is incorrect as it changes the meaning by using the passive voice 'has been completed' instead of the active voice. Choice D is incorrect as 'complete' should be 'completed' to match the present perfect tense.

Correct Answer: B

Rationale: The correct answer is B. If someone is described as assiduous, it means they are diligent, hardworking, and persistent in their efforts. This aligns with the trait of being 'Industrious.' Choices A, C, and D are incorrect because being lazy, inconsistent, or procrastinating are the opposite characteristics of someone who is assiduous.