根据句意, 在答题卷标有题号的横线上, 写出括号内所给单词的适当形式。每空只写一词。
点M(x0,y0)在圆x2+y2=R2外,则直线x0x+y0y=R2与圆的位置关系是( )
— Because I had lots of homework to do.
胎儿在母体子宫内发育,能通过____ 和____ 从母体中获得所需的营养物质和氧。