What about No.4? I don't think it's a well-designed question.

[v0031]

It's easier to go downhill(下山) than to climb uphill, so it's easier to fall into bad habits than into good __1__. Bad habits do not come __2__. They come little by little, so you don't know their __3__. Schoolboys first pick up little bad habits at __4__ or in the streets. When they can't do their homework, they copy from their __5__. If they see bigger boys smoking, they __6__ want to learn to smoke. If they see their friends gambling(赌博), they want to gamble. When they get __7__， the habits become stronger and stronger. Then they can no longer give them up. From copying, they learn to __8__； from gambling, they learn to cheat(欺骗). __9__ no one believes in them. How __10__ it is that we stop the bad habits at the beginning!
(　　)1. A. one           B. ones          C. other          D. others
(　　)2. A. slowly        B. usually      C. fast           D. suddenly
(　　)3. A. danger        B. idea           C. plan           D. hope
(　　)4. A. work           B. school        C. home        D. night

[Never Made it to Graceland]

Either B or C. I agree, it's not obvious what the answer is.

By the way, if you have any free time, would you be willing to help me with some beginning level Chinese? I've been trying to learn on my own but would appreciate a native speaker's perspective. Please send me a message if you can help.

[S019]

It's either B or C, but yeah this is really ambiguous and I don't like the question, though the word "schoolboys" leans me towards B. Having the choices for 5-8, might give some more context and might help figure it out. Another thing leaning me towards "B," is the idea of "bigger boys smoking" and "friends gambling."

[True Federalist (진정한 연방 주의자)]

Given the east Asian ethos of filial piety, the author of this quiz probably would never have considered C to be the answer to No. 4. Home is where virtue begins after all.  But as has been pointed out, in a Western mindset, B or C are both decent answers, for the sentence in isolation. However, the later sentences give enuff context to say that B is the intended answer, as the bad examples mentioned are all from outside the home.