1 They found the lecture hard_____.
A to be understood
B to understand
C for understanding
D to have been understood
2 ______,she was very brave.
A Girl as was she
B A girl as she was
C As a girl she was
D Girl as she was
3 _____round the city,we were impressed by the city's new look.
A Taken
B Taking
C To be taken
D Being taken

答案分别为B D A
请问各位大侠，这三题答案都为啥啊？？谢啦谢啦

1 涉及到了“动词不定式用主动形式表示被动含有”的一种情形。

当动词不定式的受动者/物作主语、且同时动词不定式修饰系表结构作状语时，动词不定式不用被动形式，而用主动形式。
如：The lecture is hard to understand
The question is easy to answer.
当这种结构变为宾语+宾语补足语的复合结构时，动词不定式也是用主动形式表示被动含义。
如：I felt the question easy to answer.
= I felt (that) the question was easy to answer.
I found the lecture hard to understand.
= I found (that) the lecture hard to understand.

2 涉及到了as的倒装结构引导让步状语从句的冠词使用问题。
当as用于引导让步状语从句（即表示“虽然。。。，但是。。。”的意思）时，要将动宾中的宾语或系表中的表语前提到句首，且该作宾语或表语的名词前不能使用任何冠词。

3 考核知识点：非谓语动词作状语的语态选择。
首先，要明确take sb. around some place的结构，即这里的take（带领。。。）是一个及物动词，而且we正是它的宾语，也就是说非谓语动词与句子主语构成了动宾关系，而且非谓语动词与谓语动词存在先后顺序（显然是先被带着参观，后感到印象深刻），所以应当选用过去分词作状语。