mainly的形容詞形式怎么寫

　　例句：

　　The birds live mainly on nectar.

　　這些鳥主要以花蜜為食。

　　The sea water is mainly composed of water and salt.

　　海水主要由水和鹽組成。

　　She spoke mainly when spoken to.

　　基本上只有別人對她說話時她才開口。