。
Could you let go of my arm?
Literal
Arm [object-を] release-[benefactive-くれ]-not [question-ますか].
A polite version of the release-my-arm series. ~てくれませんか ('won't you do X for me?') is the soft negative interrogative request form — the negative makes it less demanding, as in English 'won't you' vs 'will you'. 放す here emphasizes release-from-grip.