挡: 挡Ⅰ动词1.(拦住; 抵挡) keep off; ward off; block; resist 短语和例子挡道 block the road; get in the way; 挡风 shelter sth. from [keep out] the wind; 挡雨 keep off the rain; shelter one from the rain; 筑一道篱笆挡狗
保持: (维持; 使不消失或减弱) keep; hold; retain; maintain; preserve 短语和例子保持安静 keep quiet; 保持优势 hold on to a dominant [favorable] position; 保持警惕 maintain vigilance; be on the alert; 保持清洁 keep clean; 保持优良传