Being asked which way to go ,he said he had no idea.Being 是不可以少的.前一句是ing形式引导伴随状语.若没有Being,句子就应该变为“When(he was 可以省略)asked which way to go,he...”.
Being tied to the tree,he cannot escape.(此处being 做原因状语.)= Because he is tied to ...
现在进行时前面有 am /is/ are 是be 动词,being done是整个充当动词的,因动作是被动的,而am /is/ are 后面要加ing形式,因此只能be done 的 be 做ing 形式.
由此可见,being done 做状语,而am /is/ are being done 就是动作现在进行,而动作又是被动的.是谓语结构.
希望我解释通了,哈哈.