I'm studying for taking the JLPT N3 and I've run across this exercise:
この用紙は必ず黒か青のペンで記入する（_____）
Between the possible answers I had these two: もの and こと. I chose もの but the correct answer is こと.
Could anyone help me try to understand what's the difference, in this case, between this two?
So I did a little bit more research and I found this:
Verb + ことだ indicates essential ACTIONS.
Verb + ものだ indicates ideal and essential STATES.
So with this I pretty much understand the exercise but still, is there anything else I should pay attention to?
