根据句意及首字母完成单词。
He is going to the post office to buy a s     for his letter.
I think working hard is the secret of the s    .
My father often uses a f     to make her cool in the hot days.
Don’t speak to David like that. After all (毕竟) he is j     a little child.
—Thanks a lot.
—It’s my p    .