Which piece of textual evidence in "Of Mice and Men" best supports the theme of the novel?

a
"Curley's wife came around the end of the last stall. She came very quietly, so that Lennie didn't see her. She wore her bright cotton dress and the mules with the red ostrich feathers. Her face was made up and the little sausage curls were all in place. She was quite near to him before Lennie looked up and saw her" (Steinbeck).
b
"'I tol' you an' tol' you,' she said. 'I tol' you, 'Min' George because he's such a nice fella an' good to you.' But you don't never take no care. You do bad things'" (Steinbeck).
c
"'He was so little,' said Lennie. 'I was jus' playin' with him... an' he made like he's gonna bite me... an' I made like I was gonna smack him... an'... an' I done it. An' then he was dead'" (Steinbeck).
d
Lennie said, 'I thought you was mad at me, George.' 'No,' said George. 'No, Lennie. I ain't mad. I never been mad, an' I ain't now. That's a thing I want ya to know.' The voices came close now. George raised the gun and listened to the voices. Lennie begged, 'Le's do it now. Le's get that place now.' 'Sure, right now. I gotta. We gotta.'" (Steinbeck).

The piece of textual evidence that best supports the theme of the novel in "Of Mice and Men" is option b: "'I tol' you an' tol' you,' she said. 'I tol' you, 'Min' George because he's such a nice fella an' good to you.' But you don't never take no care. You do bad things'" (Steinbeck). This quote showcases the theme of the novel, which is the consequences of loneliness and isolation, by highlighting the negative effects of Lennie's actions on George and those around him.