题目内容：

麻烦帮忙分析句子结构、成分.
In the arena of space research,live animals are still practical alternatives on a flight not considered to be sufficiently safe for human astronauts.

优质解答

In the arena of space research,(地点状语)live animals （主语）are （谓语）still practical alternatives （表语）on a flight （地点状语）not considered to be sufficiently safe for human astronauts(做flight的定语）