如图，浦西对岸的高楼AB，在C处测得楼顶A的仰角为30°，向高楼前进100米到达D处，在D处测得A的仰角为45°，求高楼AB的高．

阅读短文，判断正误，正确的在题前打T，错误的打F 
Helen is an English school girl. She’s eleven years old. Now she and her parents are in Jinan. Her parents teach English in our school. They are very kind. Helen is a good pupil. She’s good at maths. We are good friends. She’s clever and beautiful . Now she can speak a little Chinese.
(1)Helen is from America.   ____ 
(2)Her parents are English teachers____ 
(3)Helen is in Beijing now.____ 
(4)She isn’t good at maths.____
(5)She can speak a lot of Chinese.____ 

小肠是消化和吸收的主要场所，其中与吸收营养物质相适应的形态结构有（  ）

①小肠长约5～6米，是消化道中最长的一段

②小肠内有许多种由消化腺分泌的消化液，如胰液、肠液等

③小肠内壁有许多皱襞，皱襞上有大量的小肠绒毛

④小肠绒毛内的毛细血管壁由一层上皮细胞构成．

一本语文书长21米．