**Rule: Understanding Idiomatic Expressions.** The idiom 'open a can of worms' means to take an action that inadvertently leads to a host of new, unforeseen troubles. The fact that the policy 'creating more problems than it solved' is a clear example of this. Option (b) is the correct definition. Option (a) is a literal interpretation. Option (c) and (d) are the opposite of the idiom's meaning.

**Rule: Understanding Idiomatic Expressions.** The term 'vested interest' refers to a strong personal reason for wanting something to happen because one will benefit from it. Owning stock in a company gives a person a direct financial reason to want the company to succeed. Option (a) is the correct definition. Option (b) is a literal misinterpretation of 'vest'. Option (c) is the opposite of a personal interest. Option (d) is the opposite of having a strong interest.

**Rule: Understanding Idiomatic Expressions.** The idiom 'the talk of the town' refers to a person or subject that is the main topic of gossip and discussion among many people in a community. A 'heroic rescue' is a newsworthy event that would generate such widespread discussion. Option (b) is the correct definition. Option (a) and (c) are the opposite. Option (d) is a different kind of 'talk'.

**Rule: Understanding Idiomatic Expressions.** The idiom 'tied up' means to be busy and unavailable. Being 'in a meeting' is a common reason for being tied up. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is the opposite. Option (d) is an unrelated detail.

**Rule: Understanding Idiomatic Expressions.** The idiom 'sworn enemies' refers to two or more people who are irreconcilably hostile towards one another. The phrase implies a deep and enduring animosity. Disagreeing on 'every issue' is characteristic of such a relationship. Option (b) is the correct definition. Option (a) is a literal interpretation of 'sworn'. Option (c) is the opposite. Option (d) is a possible but separate fact.

**Rule: Understanding Idiomatic Expressions.** The idiom 'worth one's salt' means to be competent and effective in one's job. The phrase originates from ancient Rome where soldiers were sometimes paid in salt (salarium, the origin of 'salary'). The negative form ('not worth his salt') means someone is incompetent. Option (a) is the correct definition. Option (c) is the opposite. Options (b) and (d) are literal misinterpretations.

**Rule: Understanding Idiomatic Expressions.** The idiom 'music to my ears' refers to information that is very welcome and pleasing to hear. A positive speech after a lot of 'criticism' would be very pleasing. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Options (c) and (d) are the opposite of a pleasant experience.

**Rule: Understanding Idiomatic Expressions.** The idiom 'have a field day' means to have a very enjoyable and exciting time, often by taking advantage of an opportunity to do something you like. Children 'playing in the park' would certainly consider it an enjoyable day. Option (b) is the correct definition. Option (a) and (d) are literal misinterpretations. Option (c) is the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'on the line' means to be in a situation of risk or jeopardy. A career can be 'on the line' if a scandal threatens to end it. Option (b) is the correct definition. Option (a) is a literal misinterpretation. Option (c) is the opposite. Option (d) is an unrelated outcome.

**Rule: Understanding Idiomatic Expressions.** The idiom 'a doubting Thomas' refers to a skeptical person who needs proof to believe something. The name comes from the Apostle Thomas, who doubted Jesus's resurrection until he could see and touch the wounds. The need to 'see proof' is the key characteristic. Option (b) is the correct definition. Option (a) is a misinterpretation. Option (c) is the opposite. Option (d) is a misattribution (he is a biblical figure).