**Rule: Understanding Idiomatic Expressions.** The idiom 'join forces' means to unite or combine with others to achieve a common goal. Two companies collaborating on a project is a perfect example of joining forces. Option (c) is the correct definition. Option (a) and (b) are literal, military interpretations. Option (d) is the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'in seventh heaven' (similar to 'on cloud nine') describes a state of extreme joy and elation. Getting engaged is a life event that typically causes such feelings. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is the opposite. Option (d) is a possible but not necessary interpretation.

**Rule: Understanding Idiomatic Expressions.** The idiom 'fall flat' means to fail to have the desired impact or to be completely unsuccessful. When a joke 'falls flat', it means it fails to amuse people. The fact that 'no one laughed' is a clear indication of this failure. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is the opposite. Option (d) is unrelated.

**Rule: Understanding Idiomatic Expressions.** The proverb 'you can't make an omelette without breaking eggs' means that in order to achieve a desired outcome, it is often necessary to accept some unpleasant consequences or make sacrifices along the way. It is a justification for necessary but unwelcome actions. Option (b) correctly explains this figurative meaning. Option (a) is a literal truth but not the proverb's meaning. Options (c) and (d) are pieces of advice about eggs, not the deeper meaning.

**Rule: Understanding Idiomatic Expressions.** The idiom 'go the extra mile' means to make a greater effort than is necessary in order to achieve something. Wanting to make a report 'perfect' implies a willingness to do extra work. Option (c) is the correct definition. Option (a) is a literal interpretation. Option (b) is the opposite. Option (d) is a different strategy.

**Rule: Understanding Idiomatic Expressions.** The idiom 'give the green light' means to grant permission for a project or activity to begin. It is derived from the green light of a traffic signal, which means 'go'. Option (c) is the correct definition. Option (b) is the opposite (a 'red light'). Options (a) and (d) are literal misinterpretations.

**Rule: Understanding Idiomatic Expressions.** The idiom 'a dark horse' refers to a person who wins a race or competition despite being previously unknown or not expected to win. The fact that 'nobody expected him to win' is the key element of this idiom. Option (b) is the correct definition. Option (a) is a literal interpretation. Option (c) describes a favorite, the opposite of a dark horse. Option (d) is unrelated.

**Rule: Understanding Idiomatic Expressions.** The idiom 'like two peas in a pod' is used to describe two people who are very similar in looks, behavior, or interests. Having the 'same interests and opinions' is a clear example of this similarity. Option (c) is the correct definition. Option (a) is the opposite. Option (b) and (d) are literal misinterpretations.

**Rule: Understanding Idiomatic Expressions.** The idiom 'a drop in the ocean' (or 'a drop in the bucket') refers to an amount that is so small as to be insignificant or have very little effect. A small, independent bookstore's sales would be insignificant compared to a giant online retailer's. Option (c) is the correct definition. Option (a) is the opposite. Option (b) is the literal meaning. Option (d) is an unrelated detail.

**Rule: Understanding Idiomatic Expressions.** The idiom 'take something with a grain (or pinch) of salt' means to view something with skepticism and not to interpret it literally or believe it completely. It suggests that the information may be exaggerated or unreliable. Option (b) is the correct definition. Option (a) and (d) are literal misinterpretations. Option (c) is the opposite.