—Where's Sam?
—He _______ for a test in his room.
A：study
B：studies
C：studied
D：is studying
成年人平静时每分钟的呼吸频率是（ ）
植物体内的水分是根部从土壤中吸收的，水分能从根部运到高大树木的顶端是因为（ ）
— I missed the beginning of ________ cartoon The Lion King.— What a pity! You should leave school half _______ hour earlier.
