___ several times,but he still doesn't know how to use the cleaner.a.Having been shown b.I have shown him 为什么用B不用A
问题描述：
___ several times,but he still doesn't know how to use the cleaner.
a.Having been shown b.I have shown him 为什么用B不用A
答
我已经演示给他看好几遍了但是他还是不懂怎么用
答
是选B
给你简单说说：
楼主选A的解释应该是（现在）分词做状语,但请看后面还有一个but.按楼主的思路,此句应为：
Having been shown several times,he still doesn't know how to use the cleaner.对吧,不能有but.
所以此处就是一个简单的but转折句.
“我和他说了好多次,但他仍然不知道怎样用清洁器.