This kind of flower comes out and () red in spring.

A是正确答案
这两个词都可以翻译成become 变成,但是有所不同
turn主要指颜色上的变化,可以指物体颜色发生变化,也可以指人因为感情或情绪的原因皮肤或脸色改变,也常用来指人年纪大了之后,头发变白或变灰
而get则表示从一种状态或一种感情变成另外一种,也可以表示天气变暖或变冷等等.
给你一些例子：
When I tried to talk to him about it,he just got really angry.
It's getting quite chilly out there.
The clothes all turned pink in the wash.
Every time Jim speaks to Jane,he turns bright red.
Her face was lined and her hair was already turning grey.

A
turn red为变红，是过程变化
强调变化

a...

A
别搞那么复杂了，就是“自发的变（色）”用turn。
get可以指“被改变”的意味。

AAAAAA

A