Fill in the blank given below using the correct idiom. Susan decided to _______________ by joining the team of volunteers for the charity event, allowing her to help others and socialize at the same time.

The idiom "kill two birds with one stone" means to achieve two objectives or complete two tasks with a single action. (A) sink her teeth into: To fully engage with or become deeply involved in something. (B) take with a grain of salt: To be skeptical or not fully believe something. (C) kill two birds with one stone: Achieve two objectives or complete two tasks with a single action. (D) roll up her sleeves: To get ready to work, especially on a task that requires effort. (E) stand in good stead: To be beneficial or advantageous in the future.