Why would shikamaru and ino go for incorrect answeers they could avoid the trouble by answering by themselves since its not correct .
It was implied to be correct by both sakura and ino and there is nothing suggest otherwise so Your statement needs proof or it isn't vaild.
No one could even understand the question. Let's take this for example.
You are giving a test and almost no one in your class can even understand the question. But there are a couple of book nerds who do understand the question but dont know the answer and you have to get the answer correct anyhow.
What would you do? Of course you'd try to cheat from the two nerds who understand the question even though they dont know the answers. Thats the best way to get some marks.
Thats the same thing which happened in the chunin exams.
You ask for proof? What proof do you have that those answers were correct? Just because it was implied to be correct doesnt mean they are.