1.表示原因1)Therearethreereasonsforthis.2)Thereasonsforthisareasfollows.3)Thereasonforthisisobvious.4)Thereasonforthisisnotfartoseek.5)Thereasonforthisisthat.6)Wehavegoodreasontobelievethat.例如：Therearethreereasonsforthechangesthathavetakenplaceinourlife.Firstly，peopleslivingstandardhasbeengreatlyimproved.Secondly，mostpeoplearewellpaid，andtheycanaffordwhattheyneedorlike.Lastbutnotleast，moreandmorepeopleprefertoenjoymodernlife.注：如写第一个句子没有把握，可将其改写成两个句子。如：Greatchangeshavetakenplac
