The new manager hit rock bottom after securing a massive

Solution

The idiom "hit rock bottom" means to reach the lowest possible point, which contradicts the sentence's positive context. "Struck gold" means to achieve great success or luck, which fits the meaning correctly.The idiom "hit rock bottom" means to reach the lowest point, usually in a negative sense. However, the sentence describes a positive outcome, so "struck gold" (meaning to find great success or wealth unexpectedly) fits the context better.Meanings of other idioms:Climbed the ladder – Progressed upward, especially in a career.Turned the tables – Reversed a situation, often from disadvantage to advantage.Got cold feet – Became nervous or hesitant, typically about an important decision.Since the new manager's success is related to a massive deal that boosted profits, option (b) is the correct replacement.