三种基本形式 If had a bike.I would lend it to you(f从句用过去时,主句用 should/ would/ could/ mighti不定式) If he had been here he would have helped you(从句过去完成时,主句 should would/ could/ might+不定式完成时) I would do it some other wa(从句用 should/ were to3主句用 should/woud could /might+不定式)
在 There be句型中 There is no smoke without fire There seems to be little time left There,here结构中,如果主语有好几个,谓语动词 与最邻近的主语一致。 There was a TV set, a portrait and several albums on the shelf
Atomic Structure All natural and most synthetic substances on earth are made from the ninety naturally occurring chemical elements. An atom is the smallest particle into which an element can be divided while still retaining the chemical characteristics of that element (fig 3. 1). The nucleus, at the center of the atom contains one or more particles with a positive electrical charge(protons fif and usually some particles of similar mass that have no charge(neutrons