grateful解釋：
    感激的，感謝的;令人愉快的;宜人的
    grateful語法：
    adj.形容詞
    grateful同義詞：
    grateful，thankful，appreciative
    grateful造句：
    I should like to extend my grateful thanks to all the volunteers.我想對所有的志愿者致以衷心的謝意。
    grateful考試真題：
    I'm very grateful to you for your assistance.
    A.helpful B.hopeful
    C.pitiful D.thankful
    「答案」D
    「解析」考察固定搭配。be grateful to 感謝，感激;be thankful to 感謝，感激;be helpful for 對……有幫助