请问have collected 和have been collecting 有什么区别

请问have collected 和have been collecting 有什么区别 have been doing 和have+过去分词有什么不同?RT 比如have been collecting 和have collected的不同之处 I have been collecting shells for three years.和 I have collected shells for three years.在语法和意 I have been collected shells since Isaw her.和I have been collecting shells since I saw her哪个对? I find phone cards beautiful .I ______ them for many years .A.had collected B .had been collected C .have been collectedD .have been collecting 请问选哪一项 为什么要这样选, I have been collected stamps these yeas.与I have collected stamps.有什么区别? I ＿ over 2500 kinds of stamps so far.A.collected B.have collecting C.have collected D.have beenD.have been collected Have you ever collected _____填anything还是something They have collected stamps since 1986.改为被动语态 Have I ever collected waste paper or bottles for recycling? Tom has collected ____stamps as I have .A.twice as many B.twice so manyA和B之间有什么区别? 计量单位请问a.i.g/hm2和ga.i./ha分别是什么单位? 请问邵尔硬度Shore A(HA)和硬度计算单位(kg/mm2)如何换算?有没有换算公式? ----How many stampe have you collected so far?----__ ___ ___ ____(300多张) the scientists have collected much____about the south pole.A advice B opinions C storiesD information 翻译 The works of art have been collected by the people of France over many centuries 连词成句 more stamps have than two collected l hundred 怎么连啊；；；；；；；；； Is a beautiful girl and have never seen such a beautiful,Ha ha