They found the text hard to underwstand

they found the lecture hard ____.

\u8fd9\u4e2a\u5b9e\u5b9e\u9645\u7b49\u4e8e\u590d\u5408\u53e5\uff1a
They found that the lecture was hard to understand.

\u6ce8\u610f\u8fd9\u4e2a\u53e5\u578b\uff1a
\u4e3b\u8bed+be+ \u5f62\u5bb9\u8bcd+to do(\u53ca\u7269\u52a8\u8bcd\uff09
\u6b64\u53e5\u578b\u53e5\u5b50\u7684\u4e3b\u8bed\u662fto do \u7684\u903b\u8f91\u5bbe\u8bed\uff0c \u6240\u4ee5\u4e0d\u5b9a\u5f0f\u4e0d\u80fd\u7528\u88ab\u52a8\u5f0f\u3002
\u5982\uff1a
English is easy to learn
I find that Wnglish is easy to learn(\u5bbe\u8bed\u4ece\u53e5\uff09
=I find English easy to learn (\u590d\u5408\u5bbe\u8bed\uff09

\u5982\u4e0d\u660e\u767d\u8bf7\u8ffd\u95ee\uff0c\u5982\u679c\u6ee1\u610f\u8bf7\u91c7\u7eb3
\u624b\u673a\u63d0\u95ee\u8005\u5982\u679c\u6ee1\u610f\uff0c\u8bf7\u5728\u5ba2\u6237\u7aef\u53f3\u4e0a\u89d2\u8bc4\u4ef7\u70b9\u201c\u6ee1\u610f\u201d\u5373\u53ef
\u5982\u679c\u6709\u5176\u4ed6\u95ee\u9898\u8bf7\u91c7\u7eb3\u672c\u9898\u540e\u53e6\u53d1\u70b9\u51fb\u5411\u6211\u6c42\u52a9\uff0c\u7b54\u9898\u4e0d\u6613\uff0c\u8bf7\u8c05\u89e3\uff0c\u8c22\u8c22\u3002
\u795d\u5b66\u4e60\u8fdb\u6b65

\u9009B \u76f8\u4fe1\u6211\u3002
\u9996\u5148\uff0c\u76f4\u63a5\u9009\u7684\u529e\u6cd5\uff0c\u4e00\u822c\u90fd\u8bf4hard to understand\uff0c\u56e0\u4e3aunderstand\u7684\u662fthey \uff0c\u6240\u4ee5\u662f\u4e3b\u52a8\u8bed\u6001\u3002
\u5176\u6b21\uff0c\u6392\u9664\u6cd5\uff0cA\u4e00\u5b9a\u9519\uff0c\u5373\u4f7f\u7528\u88ab\u52a8\u8bed\u6001\uff0c\u4e5f\u662fto be understood \uff0c\u6ca1\u6709under standed \u3002\u800cCD\u7528\u7684\u4ecb\u8bcdfor \uff0c\u540e\u5e94\u5f53\u63a5sb.\u7684\u5bbe\u683c\u3002
\u6240\u4ee5\u9009B\u3002
\u5efa\u8bae\u8bb0\u4f4fIt's not hard for us to understand English .
\u518d\u6b21\uff0c\u7528\u8bed\u611f\uff0c\u4e5f\u53ea\u6709B\u8bfb\u8d77\u6765\u987a\u53e3\u3002
\u5e0c\u671b\u6211\u7684\u56de\u7b54\u80fd\u4e3a\u4f60\u5e26\u6765\u5e2e\u52a9;-)

选：B. hard to understand
这句话的意思是：他们发现这篇课文很难理解。
be/系动词+sth+hard to do: 某事很难做
found the text hard to understand=发现这篇课文难理解

A
understand 和text 的关系是被动关系，所以选择A
B是主动关系
C for understanding
D 不合语法

found是find的过去式
find sth+adj+to do 是固定用法，意为发现\觉得什么怎么样
（sth:某物，adj:形容词）

扩展阅读：they paid money for the ... the iasb says ... they found that after a ... in the19th century ... they found the latest ... the fun they have ... they found the lecture ... the patient the doctors ... they found the boy dead ...