日本に来___ばかりなので、まだ何も分かりません。
Q. Which form completes 'I've only just come to Japan'?
Translation
I've only just arrived in Japan, so I don't know anything yet.
Explanation
〜たばかり (plain past + ばかり) means 'just did': 来たばかり. 来るばかり would mean 'all that's left is to come', a different pattern.