系统解析:这是说每天every day做的事情用一般现在时, 主语是大量的申请信Plenty of application letters(plenty of表示大量的), 处理deal with, 主语是其承受者, 构成被动语态, 故用一般现在时的被动语态am/is/are+过去分词, 主语是可数名词复数, 故are, deal的过去分词是dealt, 及时in time, 故答案是Plenty of application letters are dealt with in time every day.