Final answer:
The 'new' Hard Rock in Etheridge Knight's poem is compared to an old dog that has been beat too much, showing a sense of defeat.
Step-by-step explanation:
In the poem “Hard Rock Returns to Prison from the Hospital for the Criminal Insane” by Etheridge Knight, the speaker compares the 'new' Hard Rock to an old dog that has been beat too much, which indicates a sense of defeat and lost resistance. The once rebellious and strong-willed Hard Rock, after being subjected to a lobotomy, returns to the prison population significantly subdued. None of the other options, such as an empty sack or a gelded stallion, are used in this comparison within the poem. Therefore, the correct answer is option 1) An old dog that has been beat too much.