Answer:
They could not understand the writing
Step-by-step explanation:
Logically, this is the most likely option. The chinese language is very complex, and is comprised of complex symbols, very much unlike the english language. Though the immigration officers might have communicated a lot with chinese people, it was unlikely that they understood the writing, or even wanted to (based on the attitude they had).
Process of elimination:
C - It never says that there was grafitti at Ellis island, therefore we can deduce this is not the answer (most likely)
D - The fact that the immigrants were from china is important, but does not explain why the officers dismissed the writing as grafitti.
B - This is the next most likely option, but I chose A over it because it makes the most sense (logically) Its hard to pick though, because it also never states that the writing was in chinese characters, but I chose A anyway because there's a higher chance they would write something in their own language to either, 1, prevent the officers from understanding, or 2, prevent the writing from offending any officers (which would have been possible, had they understood what it meant in english)
There's a lot more reasons why A is the best choice, but heres a basic rundown.