下面是联合国发行的“联合我们的力量”邮票中的主体图形，请写出构图要素，并说明图形寓意，要求语意简明，句子通顺，不超过85个字。

(1) How many units must we learn this term? （改为被动语态）
How many units____ this term?
(2)It took him two hours to finish reading the novel.（改为同义句）
He ____ two hours____ the novel.
(3)Parents should allow their children to choose their own clothes.(改为被动语态)
Children ____ to choose their own clothes.
(4)I was asked to clean up the room by my teacher.（改为主动语态）
My teacher____ to clean up the room.
(5)I believe that Lucy is allowed to perform a play for the old people.（改为否定句）
I____ believe that Lucy____  to perform a play for the old people.