**Rule: Understanding Idiomatic Expressions.** The idiom 'a wolf in sheep's clothing' refers to someone who appears to be friendly and harmless but is actually hostile and malicious. The sentence itself explains the meaning by contrasting 'pretending to be a friend' with 'secretly working against you'. Option (b) is the correct definition. Option (a) is a literal interpretation. Option (c) is the opposite. Option (d) is an unrelated profession.

**Rule: Understanding Idiomatic Expressions.** The idiom 'turn over a new leaf' means to reform and begin a new and better course of life. Being released from prison is often a catalyst for such a change. Option (c) is the correct definition. Option (a) and (d) are literal misinterpretations. Option (b) is the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'set in stone' means to be fixed and impossible to change. The sentence uses the negative form ('not set in stone') to mean the opposite: that the rules *are* changeable. Therefore, the idiom itself means unchangeable. Option (c) is the correct definition of the idiom. Option (b) defines the situation in the sentence. Option (a) is a literal interpretation. Option (d) is a possible but separate quality.

**Rule: Understanding Idiomatic Expressions.** The idiom 'paint the town red' means to go out and celebrate in a wild and exuberant manner. Celebrating a 'reunion' is a perfect occasion for such a lively celebration. Option (a) is the correct definition. Option (b) is a literal misinterpretation. Option (c) is the opposite. Option (d) is a different kind of activity.

**Rule: Understanding Idiomatic Expressions.** The idiom 'the salt of the earth' refers to a person or group of people of great worth and reliability. The description of being 'honest and willing to help' defines such a person. Option (b) is the correct meaning. Option (a) and (d) are literal misinterpretations. Option (c) is the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'put the cart before the horse' means to do things in the wrong sequence. Logically, a horse pulls a cart from the front. The example of booking a venue without a date is a clear example of doing things in the wrong order. Option (a) is the correct definition. Option (b) is the literal, correct order. Option (c) is the opposite of the idiom's meaning. Option (d) is an unrelated action.

**Rule: Understanding Idiomatic Expressions.** The idiom 'have one's head in the clouds' is used to describe a person who is a daydreamer and is not grounded in reality. Not paying attention to 'practical details' is a key characteristic of such a person. Option (b) is the correct definition. Option (a) and (d) are literal misinterpretations. Option (c) is the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'by the skin of one's teeth' means to barely manage to do something. The presence of 'many other qualified candidates' suggests that his success was very narrow. Option (a) is the correct definition. Option (b) is the opposite. Option (c) is a literal misinterpretation. Option (d) is a possible but not implied meaning.

**Rule: Understanding Idiomatic Expressions.** The idiom 'pay lip service' means to show support for something in words only, not through actions. It implies insincerity. This is a common criticism leveled at politicians. Option (a) is the correct definition. Option (b) is a literal misinterpretation. Option (c) is the opposite. Option (d) means to be silent, not to speak insincerely.

**Rule: Understanding Idiomatic Expressions.** The idiom 'cabin fever' refers to the distressed and irritable feeling that results from being isolated or confined for an extended period. Being 'stuck indoors for three days' is a common cause of this feeling. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is the opposite feeling. Option (d) is unrelated.