—Are the beaches in Dalian beautiful?
—Sure. They___________ lots of tourists from home and abroad every year.
A:promise
B:advise
C:attract
D:tell
若x,y∈R+且2x+y=1,则 1x+1y 的最小值( )
青青草原生态系统中,一条食物链中三种生物的数量比例图如图,若丙被人类大量捕杀,一段时间内乙的数量变化曲线是( )