Meaning: 'Result' refers to an outcome or effect that follows from a particular cause or action.

Wrong options:

• reaction: 'Reaction' is a noun that refers to a response to a stimulus, but it does not fit the context of being an outcome of changes.
• passes: 'Passes' is a verb that does not fit grammatically in this context as it does not indicate an outcome.
• signal: 'Signal' is a noun that refers to a sign or indication, but it does not convey the idea of an outcome.
• amount: 'Amount' is a noun that refers to a quantity, which does not relate to the outcome of chemical changes.
• cause: 'Cause' is a noun that indicates a reason for something, which is the opposite of what is needed here as we are looking for an outcome.
• usage: 'Usage' is a noun that refers to the way something is used, which does not fit as an outcome of chemical changes.
• symbol: 'Symbol' is a noun that represents something else, but it does not relate to the outcome of chemical changes.

Correct answer: signal

Explanation: The term 'signal' is appropriate as it is a noun that describes the indication or message that is transmitted from one neuron to another. It fits grammatically and contextually as it follows the phrase 'causing a.'

Meaning: 'Signal' refers to a message or indication that is communicated, particularly in the context of physiological processes.

Wrong options:

• storage: 'Storage' is a noun that refers to the act of keeping something, which does not fit the context of transmitting a message.
• reaction: 'Reaction' refers to a response, which does not align with the idea of a message being passed.
• passes: 'Passes' is a verb that does not fit as it does not describe a noun indicating a message.
• amount: 'Amount' refers to a quantity, which does not relate to the concept of signaling in physiology.
• result: 'Result' indicates an outcome, which does not fit the context of a message being transmitted.
• cause: 'Cause' refers to a reason for something, which does not fit as it does not describe a message.
• symbol: 'Symbol' refers to a representation, which does not convey the idea of a physiological message.

Correct answer: storage

Explanation: The word 'storage' fits as it is a noun that describes the act of keeping or holding something, which in this case refers to oxygen in the blood. It aligns grammatically and contextually with the phrase 'include the.'

Meaning: 'Storage' refers to the act of keeping or holding something for future use, particularly in a biological context.

Wrong options:

• signal: 'Signal' refers to a message or indication, which does not fit the context of holding oxygen in the blood.
• reaction: 'Reaction' refers to a response, which does not relate to the concept of holding or storing oxygen.
• passes: 'Passes' is a verb that does not fit as it does not describe the act of holding something.
• amount: 'Amount' refers to a quantity, which does not convey the idea of storage.
• result: 'Result' indicates an outcome, which does not fit the context of holding oxygen.
• cause: 'Cause' refers to a reason for something, which does not relate to the act of storage.
• symbol: 'Symbol' refers to a representation, which does not convey the idea of holding oxygen.

Correct answer: passes

Explanation: The verb 'passes' is appropriate as it describes the action of oxygen moving through the lungs. It fits grammatically and contextually as it follows the subject 'it' referring to oxygen.

Meaning: 'Passes' refers to the action of moving through or across a space, particularly in the context of oxygen traveling through the lungs.

Wrong options:

• storage: 'Storage' is a noun that does not fit as it does not describe an action.
• signal: 'Signal' is a noun that does not relate to the action of moving through the lungs.
• reaction: 'Reaction' refers to a response, which does not fit the context of movement.
• amount: 'Amount' refers to a quantity, which does not convey the action of passing.
• result: 'Result' indicates an outcome, which does not fit as an action in this context.
• cause: 'Cause' refers to a reason for something, which does not relate to the action of passing.
• symbol: 'Symbol' refers to a representation, which does not convey the action of movement.

Correct answer: usage

Explanation: The term 'usage' fits as it is a noun that describes the act of using something, which in this case refers to the utilization of oxygen throughout the body. It aligns grammatically and contextually with the phrase 'for.'

Meaning: 'Usage' refers to the manner in which something is used, particularly in a biological context.

Wrong options:

• storage: 'Storage' refers to the act of keeping something, which does not fit the context of utilizing oxygen.
• signal: 'Signal' refers to a message or indication, which does not relate to the act of using oxygen.
• reaction: 'Reaction' refers to a response, which does not fit the context of usage.
• amount: 'Amount' refers to a quantity, which does not convey the idea of usage.
• result: 'Result' indicates an outcome, which does not fit the context of utilization.
• cause: 'Cause' refers to a reason for something, which does not relate to the act of usage.
• symbol: 'Symbol' refers to a representation, which does not convey the idea of using oxygen.