腕をまっすぐ伸ばしなさい。

arm; skill; efforts; ability

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

straight (ahead); direct; upright; erect; straightforward; honest; frank

to grow long (e.g. hair, nails); to lengthen; to extend; to stretch; to reach out; to hold out; to straighten; to smooth out; to spread evenly (dough, cream, etc.); to dilute; to thin out; to postpone; to prolong; to strengthen; to develop; to expand

to do