三下乡a program under which officials, doctors, scientist and college students go to the countryside to spread scientific and literacy knowledge and 就这样我也不知道了O(∩_∩)O~...
你好.am.is.are都是be动词,都有“是”的意思.am用于第一人称后,如:I am a teacher，而is用于第三人称单数和单数名词后,如:He is a student，are用于第二人称和复数名词后,如:Students are studying.在疑问句be动词应放于句首.and和，用于肯定句中,or或,用于否定句中,but但是,表转折.at...
