Meaning: Flexible means capable of bending easily without breaking.

Wrong options:

• resistant: Resistant implies the ability to withstand something, but it does not convey the necessary quality of bending, making it unsuitable here.
• expensive: Expensive refers to high cost, which is irrelevant to the physical properties of materials needed for quake resistance.
• opposed: Opposed means to be against something, which does not relate to the characteristics of materials in this context.
• recent: Recent refers to something that has happened not long ago, which does not describe the quality of materials.
• force: Force is a noun that refers to strength or energy, which does not fit as a description of materials.
• reduce: Reduce is a verb that means to make smaller or less in amount, which does not describe a quality of materials.

Correct answer: reduce

Explanation: The verb 'reduce' fits grammatically as it describes the action of lessening the impact of ground vibrations. Contextually, it aligns with the goal of using rubber and steel to mitigate earthquake effects.

Meaning: Reduce means to make something smaller or less in amount, degree, or size.

Wrong options:

• flexible: Flexible is an adjective that describes materials, not an action, making it unsuitable for this blank.
• force: Force is a noun that does not convey the action of lessening impact, thus it does not fit here.
• expensive: Expensive is an adjective that describes cost, which is irrelevant to the action of mitigating vibrations.
• opposed: Opposed is a verb that means to resist or be against, which does not relate to the action of reducing impact.
• recent: Recent is an adjective that describes time, not an action, making it inappropriate for this context.
• security: Security is a noun that refers to safety, which does not convey the action of reducing impact.

Correct answer: recent

Explanation: The word 'recent' is an adjective that describes the latest designs, fitting grammatically as it modifies 'designs' and contextually aligns with the discussion of advancements in building technology.

Meaning: Recent means having happened or started not long ago; it refers to the latest developments.

Wrong options:

• flexible: Flexible describes a quality of materials, not a time frame, making it unsuitable here.
• force: Force is a noun that does not relate to the timing of designs, thus it does not fit.
• reduce: Reduce is a verb that describes an action, not a time descriptor, making it inappropriate for this blank.
• expensive: Expensive is an adjective that describes cost, which does not relate to the timing of designs.
• security: Security is a noun that refers to safety, which does not describe the timing of designs.

Correct answer: force

Explanation: The verb 'force' fits grammatically as it describes the action the computer would take to shift the building. Contextually, it aligns with the mechanism of smart buildings responding to vibrations during an earthquake.

Meaning: Force means to make something happen or to compel action.

Wrong options:

• flexible: Flexible is an adjective that describes materials, not an action, making it unsuitable for this blank.
• recent: Recent is an adjective that describes time, which does not fit as an action in this context.
• reduce: Reduce is a verb that means to lessen, which does not convey the action of compelling a shift in this scenario.
• expensive: Expensive is an adjective that describes cost, which is irrelevant to the action of shifting a building.
• security: Security is a noun that refers to safety, which does not describe an action.

Correct answer: security

Explanation: The noun 'security' fits grammatically as it serves as the object of the sentence, indicating the level of safety provided by the new designs. Contextually, it aligns with the aim of enhancing safety in earthquake-prone cities.

Meaning: Security refers to the state of being free from danger or threat; it implies safety.

Wrong options:

• flexible: Flexible is an adjective that describes materials, not a state of safety, making it unsuitable here.
• force: Force is a noun that refers to strength or energy, which does not relate to the concept of safety.
• reduce: Reduce is a verb that describes an action, not a state of being, making it inappropriate for this blank.
• expensive: Expensive is an adjective that describes cost, which does not relate to the concept of safety.
• recent: Recent is an adjective that describes time, which does not fit as a measure of safety.