“What makes you think the test will only have one correct answer per questions?”
Oh, so you want judges to decide whether the answers are right or wrong. And who chooses the judges? Shall we have a federal commission of history judges? And who picks the people who run the commission? That looks like part of the Executive Branch. So you’ll have Mr. Trump picking the experts who judge historical truth.
“It’s not only the content of the answer but also the ability to formulate a complete answer grammatically (full sentences etc.)”
Yes, Mr. Trump is the ideal person to select people who can judge the quality of the English writing.
Oh, and by the way, in the first sentence I quoted above, you made a grammatical error in using the plural “questions”. Therefore, you just lost the right to vote. 😀
“Also do you mean to say that all history is subjective and that there is no objective truth in it?”
There are some historians who argue that case. There is some merit to the notion that historical analysis includes a subjective element. However, I believe that it is possible to get a fairly good objective approximation of the truth. But you have to leave politics out of it, because politics is far and away the most distorting factor in historical analysis. You appear to be unaware of the role politics plays in the representation of history. I suggest that you google “textbook controversies” to get an idea of how nasty this problem is.