短語部分沒有獨立主語，則短語結(jié)構(gòu)稱為非謂語動詞。
    非謂語動詞的結(jié)構(gòu)：分詞(分詞短語)
    句子的主語決定非謂語動詞中的分詞是用主動還是被動形式。如果是句子的主語發(fā)出動作，則使用現(xiàn)在分詞;如果動作不是由句子的主語發(fā)出，則使用過去分詞。
    43.No matter how frequently _A_， the works of Beethoven always attract large audiences.
    A performed B performing C to be performed D being performed
    perform vt. 表演，演出，演奏;
    to be performed 將要被演奏; being performed 正在被演奏;
    一些特殊的動詞：
    第一點：forget 忘記; [反義] remember 記得;
    這兩個詞后加動詞不定式表示將要進(jìn)行的行為;這兩個詞后加動詞ing形式表示已經(jīng)做過的事情。
    注意：動名詞與現(xiàn)在分詞形式一樣，但含義不同。這兩個詞后加動詞ing形式都是動名詞。
    forget to do sth. 忘記要去做某事; forget doing sth. 忘記做過某事;
    remember to do sth. 記得要去做某事; remember doing sth. 記得做過某事;
    62. I remember _B_ to help us if we ever got into trouble.
    A once offering B him once offering C him to offer D to offer him
    offer vt. 提出，提供; offer sb. sth. / offer to do sth.
    him once offering 如果改成 his once offering 也正確。