— ________ is the book sale?
— It's next week.
A:What
B:Who
C:Where
D:When
下列诗句描写春天的是( )
生态系统具有自我调节能力,但这种能力是有限的。
—他们正在扫地。
—What ____ they ____?
— They ____ ____ the floor.