19. At the tide ____ from the shore, we are able to look for shells.                
    A. preceded   B. proceeded   C. acceded   D. receded

<precede>
precede  在…之前，领先于，优先
</precede>

<recede>
recede  撤退
concede  妥协，让步
concession  让步
compromise  妥协，让步
</recede>