with+宾语+宾补,宾补只能是-ing,不定式,过去分词
D 前半句是ing做状语,用have done完成形式表示参观office这个动作发生在shown round the building动作的前面,而主语是the foreign visitors ,所以用被动式
.A person (learning a foreign language) must be able to use the foreign language 【forgetting all about his own】.
前面一个为ing短语作定语,相当于A person who is learning a foreign language
后一个是ing作状语表伴随状态,用于说明use the foreign language的状态
过去分词作定语,实际上相当于Many things that are considered
鉴定完毕