**Rule: Understanding Idiomatic Expressions.** The idiom 'straight from the horse's mouth' means that the information comes from the most direct, authoritative, or reliable source. This phrase is used to emphasize the authenticity of the information. Option (c) is the correct definition. Option (b) is the opposite (e.g., 'through the grapevine'). Options (a) and (d) are incorrect, literal interpretations.

**Rule: Understanding Idiomatic Expressions.** The idiom 'eat one's words' means to retract a statement or admit that what one said was incorrect, often in a humiliating way. If someone boasts and their team loses, they are forced to admit their prediction was wrong. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is unrelated. Option (d) would only happen if his boast was correct.

**Rule: Understanding Idiomatic Expressions.** The idiom 'a long shot' refers to an undertaking, guess, or attempt that has a very low probability of success. The phrase 'but the teacher believed him' implies that the success of the explanation was surprising and unlikely. Option (a) is the correct definition. Option (b) describes length, not probability. Option (c) is a literal meaning from photography. Option (d) is the opposite of a long shot.

**Rule: Understanding Idiomatic Expressions.** The idiom 'up in arms' means to be very angry and protesting strongly about something. A plan to build a highway through a neighborhood is a common cause for community outrage. Option (c) correctly defines this reaction. Option (a) and (d) are literal misinterpretations. Option (b) is the opposite of the community's angry reaction.

**Rule: Understanding Idiomatic Expressions.** The idiom 'in hot water' means to be in a difficult situation or in trouble, especially with someone in authority. Missing an 'important deadline' is a common reason for getting into trouble at work. Option (c) is the correct definition. Option (a) is a literal interpretation. Options (b) and (d) are the opposite of being in trouble.

**Rule: Understanding Idiomatic Expressions.** The idiom 'cross that bridge when we come to it' is a piece of advice meaning one should not worry about a potential future problem but rather face it when and if it occurs. It advises against premature worry. Option (c) correctly explains this approach. Option (a) is the opposite of the idiom's advice. Option (b) is a literal misinterpretation. Option (d) suggests avoidance, whereas the idiom suggests dealing with the problem at the appropriate time.

**Rule: Understanding Idiomatic Expressions.** The idiom 'hold water' means that a statement, theory, or argument seems to be sound, logical, and able to stand up to scrutiny. Being 'consistent with all the evidence' is a key reason why the testimony would be considered valid. Option (c) is the correct definition. Option (a) is a literal interpretation. Option (b) is the opposite. Option (d) is irrelevant.

**Rule: Understanding Idiomatic Expressions.** The idiom 'the big guns' refers to the most powerful and influential people or entities in a particular field. A small company would find it challenging to compete against such dominant players. Option (b) is the correct definition. Option (a) and (c) are literal interpretations. Option (d) is the opposite of what 'big guns' implies.

**Rule: Understanding Idiomatic Expressions.** The idiom 'to have a chip on one's shoulder' means to have an angry or resentful attitude, often because of a perceived past injustice. The feeling of not getting 'the same opportunities' is the source of this resentment. Option (c) correctly defines this attitude. Option (a) and (d) are literal interpretations. Option (b) is a different kind of attitude, not one born of resentment.

**Rule: Understanding Idiomatic Expressions.** The idiom 'living on borrowed time' means to continue to live or exist beyond the point at which one was expected to die or cease to exist. A 'serious illness' often leads to a prognosis that the person has outlived. Option (a) is the correct definition. Option (b) and (c) are different concepts related to borrowing and time. Option (d) is the opposite of the precarious situation implied by the idiom.