**Rule:** The noun 'confidence' is followed by the preposition 'in'. 'Confidence in' means to have a strong belief in someone's abilities or qualities. She has confidence in her own abilities, so 'in' is the correct preposition. Options (b), (c), and (d) are incorrect.

**Rule:** The adjective 'fatal' is followed by the preposition 'to'. 'Fatal to' means to cause or end in death or disaster. His behavior is fatal to his own career, so 'to' is the correct preposition. Options (b), (c), and (d) are incorrect.

**Rule:** The adjective 'responsible' is followed by 'for' or 'to'. 'Responsible for' something means to have control and authority over it and the duty of taking care of it. She is responsible for her actions, so 'for' is the correct preposition. 'Responsible to' is used to show who someone is responsible to. Options (c) and (d) are incorrect.

**Rule:** The verb 'contributing' is followed by the preposition 'to'. 'Contributing to' means to give something, especially money, in order to help achieve or provide something. He is contributing to the charity, so 'to' is the correct preposition. Options (b), (c), and (d) are incorrect.

**Rule:** The adjective 'concerned' is followed by 'about', 'with', or 'for'. 'Concerned about' means to be worried about something. He is concerned about his son's future, so 'about' is the correct preposition. 'Concerned with' means to be involved in something. 'Concerned for' means to be worried about someone's safety. Option (d) is incorrect.

**Rule:** The adjective 'astonished' is followed by the preposition 'at'. 'Astonished at' is used to express surprise about an event or a thing. His sudden resignation was the event that caused astonishment, so 'at' is the correct preposition. Option (b) 'by' is used when the cause of astonishment is a person. Option (c) 'with' is incorrect. Option (d) 'on' is grammatically incorrect.

**Rule: Understanding Idiomatic Expressions.** The idiom 'barking up the wrong tree' means to be following a false lead or misdirecting one's efforts or blame. It comes from hunting, where a dog might bark at the base of a tree where it thinks its quarry is, even after the animal has escaped. Blaming the wrong department for one's own error is a perfect example. 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 'hang in the balance' means that the future of something is uncertain and depends on the outcome of a particular event. Awaiting a crucial court decision would put a company's future in this precarious state. Option (c) is the correct definition. Option (a) is a literal misinterpretation. Options (b) and (d) are the opposite.

**Rule: Understanding Idiomatic Expressions.** The idiom 'a way with words' describes a person who has a talent for using language effectively and eloquently. The ability to make a boring subject interesting is a clear demonstration of this skill. Option (a) is the correct definition. Option (b) is a literal misinterpretation. Option (c) is the opposite. Option (d) is a profession related to words, but not the meaning of the idiom.

**Rule: Understanding Idiomatic Expressions.** The idiom 'ups and downs' refers to the mixture of good and bad experiences that happen in life or in a relationship. The statement implies that the friendship has endured through both fortunate and difficult periods. Option (b) is the correct definition. Option (a) and (d) are literal misinterpretations. Option (c) is an incomplete picture.