表示抽象意义的“困难”时为不可数;表示具体的“难题、难事”时为可数;have difficulty (in) doing sth.= have trouble (in) doing sth. 做某事有困难
train训练,trained 为过去分词,可做定语,意为“受过训练的”a trained dog
be excited about sth. 对某事感到兴奋 ,Everyone is excited about the good news.
excited 意为 兴奋的,修饰人;exciting 意为 令人兴奋/激动的,修饰物
change变化,改变 It’s hard for a person to change his life(style). 变化;零钱
change A for B 用 A 换成 B:When you travel in China, remember to change US dollars for RMB.
repair 修理,修补; fix安装;使固定 Peter ,could you please take out the trash? 彼得,你能把垃圾倒了吗?