【两道英语语法题.1.withmoreforestsbeingdestroyedinthatarea,hugequantitiesofland_______desertseachyear.A.hasbeenturnedintoB.arebeingturnedinto.为什么答案是B可以理解正在转变为沙漠,但为什么A不可以,它】

　　两道英语语法题.

　　1.withmoreforestsbeingdestroyedinthatarea,hugequantitiesofland_______desertseachyear.

　　A.hasbeenturnedintoB.arebeingturnedinto.

　　为什么答案是B可以理解正在转变为沙漠,但为什么A不可以,它不是表示从以前开始,并延续下去,且侧重对事物的影响吗?这不是A更确切?

　　2.thesuperhybridricearoundtheworld_______thelivesofmillionsofpeoplesufferingfromhungertoagreatlevel.

　　A.haveimprovedBhadbeenimproving.

　　A和B到底有什么区别啊?应该选哪个?