Grandma is ill. I have to _________ her at home.
A:look for
B:look up
C:look at
D:look after
下列运算正确的是( )
智能温室无土栽培作物,易于管理,优质高产,该项技术广泛应用于现代农业。请判断下列相关叙述中,正确的是 ( )
用半径为6的半圆围成一个圆锥的侧面,则圆锥的底面半径等于