Explanation:

- In the sentence, "With his back to the old man, he stood at the window, fists clenched, and his shoulders ______ with his choked sobbing," the context suggests a physical reaction to intense emotion.

- Option 1: shivered - implies light trembling, usually from cold or fear. It can fit but isn't the most precise choice for sobbing.

- Option 2: shook - means a more vigorous motion, which aligns with the intensity of choking sobs. Correct Answer

- Option 3: vibrated - suggests a rapid, continuous motion, typically used for objects or technical contexts rather than human emotion.

- Option 4: moved - is too general and doesn't convey the intensity of the motion described.