I am pretty sure it is because they thought they where not big enough to fight him so they where afraid...
Answer:
I think one thing Steinbeck is trying to get his readers to understand is that people need each other, even if the relationships may not fit the conventional paradigm that society might expect.
Explanation:
George and Lennie are the obvious example here. One man is short and "street-wise", while the other man is huge and simple-minded. All the same, the two men need each other, compliment one another (one provides "the brains", the other provides "the brawn"), and share a common dream.
I believe that number one is E, number 2 is A, and number three is C.
