Correct option is B
The idiom "grasping at straws" means making a desperate attempt to succeed or find a solution when all other options have failed. It often implies a sense of futility and hopelessness. Therefore, the most appropriate meaning is: (b) Desperate attempt to succeed.
· For example, when the company was on the brink of bankruptcy, the CEO started grasping at straws, proposing wild and unfeasible ideas to save it.