Meaning: 'Check' means to examine or verify something, in this case, the amount of space left in the shoe.

Wrong options:

• prove: 'Prove' implies demonstrating the truth of something, which does not fit the context of monitoring size.
• inspect: 'Inspect' suggests a detailed examination, which is more intensive than what the sensors are doing here.
• confirm: 'Confirm' means to verify the truth or accuracy of something, but it does not convey the ongoing action of monitoring.

Correct answer: room

Explanation: The word 'room' is appropriate as it refers to the available space within the shoe. It fits grammatically and contextually, as it describes the capacity that the shoe has to accommodate the foot.

Meaning: 'Room' means space or capacity available for something, in this case, the space left in the shoe for the foot.

Wrong options:

• gap: 'Gap' refers to a break or space between two things, which does not accurately describe the overall space available in the shoe.
• area: 'Area' is a broader term that could refer to a surface measurement, but it lacks the specific connotation of available space that 'room' provides.
• emptiness: 'Emptiness' suggests a lack of content, which does not fit the context of measuring available space.

Correct answer: expands

Explanation: The word 'expands' is the correct choice as it indicates the action of increasing in size, which is what the shoe does when the valve opens. It fits grammatically and contextually with the subject 'shoe' and the action described.

Meaning: 'Expands' means to increase in size or volume, which is what happens to the shoe when it adjusts to fit the foot.

Wrong options:

• emplifies: 'Emplifies' is not a standard English word and does not fit the context of size adjustment.
• develops: 'Develops' implies growth or evolution, which does not accurately describe the immediate action of size adjustment in this context.
• increases: 'Increases' could fit, but 'expands' is more specific to the physical growth of the shoe's size.

Correct answer: located

Explanation: The word 'located' is suitable as it indicates the position of the control system within the shoe. It fits grammatically and contextually, as it describes where the system is situated.

Meaning: 'Located' means to be found or situated in a particular place, in this case, inside the shoe.

Wrong options:

• sited: 'Sited' is less commonly used and does not convey the same clarity as 'located' in this context.
• established: 'Established' implies setting up or founding something, which does not fit the context of physical placement.
• laid: 'Laid' suggests placing something down, which is not the correct term for describing the position of the control system.

Correct answer: average

Explanation: The word 'average' is the correct choice as it refers to the typical size of a foot, which is relevant to the context of the shoe's design. It fits grammatically and contextually, as it describes a general measurement.

Meaning: 'Average' means the typical or mean size, which is relevant when discussing the changes in foot size throughout the day.

Wrong options:

• genera: 'Genera' is a plural term used in biological classification and does not fit the context of describing foot size.
• usual: 'Usual' refers to what is common or habitual, but it lacks the precision of 'average' in a statistical sense.
• medium: 'Medium' suggests a middle state but does not convey the same statistical meaning as 'average' in this context.