正处于生长发育时期的青少年，应多吃下列哪一组食物（　　）

(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.

ClO₂是一种消毒杀菌效率高、二次污染小的水处理剂．实验室可通过以下反应制得ClO₂：2KClO₃+H₂C₂O₄+H₂SO₄ $\underset{\_}{\underset{\_}{△}}$ 2ClO₂↑+K₂SO₄+2CO₂↑+2H₂O （方程式中H为+1价，O为﹣2价）下列说法正确的是（   ）