Meaning: 'Prove' means to demonstrate the truth or existence of something through evidence or argument.

Wrong options:

• reserve: The verb 'reserve' means to keep something for a particular purpose, which does not fit the context of establishing presence at a crime scene.
• maintain: The verb 'maintain' means to keep something in a certain state, which does not convey the action of demonstrating presence.
• evidence: The noun 'evidence' refers to the information or proof itself, but it does not fit grammatically as a verb in this sentence.
• embody: The verb 'embody' means to represent or express something in a tangible form, which does not align with the action of establishing presence.
• samples: The noun 'samples' refers to portions or examples of something, which does not fit as a verb in this context.

Correct answer: maintain

Explanation: The verb 'maintain' is appropriate here as it indicates the action of keeping or preserving a DNA database, which aligns with the context of the sentence regarding the role of the institute in London.

Meaning: 'Maintain' means to keep something in good condition or to preserve it.

Wrong options:

• prove: The verb 'prove' does not fit here as it implies establishing truth rather than the action of keeping a database.
• reserve: The verb 'reserve' means to set aside for future use, which does not relate to the action of managing a database.
• evidence: The noun 'evidence' does not fit grammatically as a verb and does not convey the action of keeping a database.
• embody: The verb 'embody' means to represent something, which does not apply to the action of managing a database.
• samples: The noun 'samples' does not fit as it refers to portions of something rather than an action.

Correct answer: samples

Explanation: The noun 'samples' fits grammatically as it refers to the pieces of DNA collected from crime scenes that can be matched with the database, making it contextually relevant.

Meaning: 'Samples' refers to portions or examples taken for analysis, in this case, DNA from crime scenes.

Wrong options:

• prove: The verb 'prove' does not fit as it does not refer to a noun that can be matched with a database.
• maintain: The verb 'maintain' does not fit as it does not refer to the items being matched but rather the action of keeping the database.
• evidence: The noun 'evidence' is too broad and does not specifically refer to the DNA pieces collected from crime scenes.
• embody: The verb 'embody' does not fit as it does not refer to physical items that can be matched.
• reserve: The verb 'reserve' does not apply as it does not refer to items collected for analysis.