不可以,只能选C
the star looks bright against the blue sky
在叔叔的画里,群星在蓝天的反衬下显得格外明亮.
因为有 looks bright,所以是在.的反衬下,用against（表对比.）
across 是有遍及的意思,但是表示有“掠过、穿过"的意思,是有动态的.
Clouds scudded across the sky.
云朵飞快地掠过天空.
A meteor suddenly shot across the sky.
一颗流星突然掠过天空.
They are moving quickly across the sky.
译文：他们快速地在空中移动.
all over常用于“all over the world全世界”
all over the sky没见过这么用的.“全天空”
如果这句是There are ...moving( )the blue sky.
填throughout the sky和through the sky都是对的,因为through有“穿过”的动态,
看几个例句体会下吧：
They rang out from far away through the sky,calling the new day.
这远方传来的钟声,划破长空,召唤着新的一页来临.
Let the flight through the sky end in to folding of the wings over the nest.
让穿越天空的飞翔以归巢敛翼作为结局.
If you face north,the sun appears to move through the sky anti-clockwise.
如果你面朝北方,太阳看来象是逆时针方向在天空运转.
而原句中looks bright看起来,是静止的状态,不能再有“穿过”的动态了.
所以across,through,throughout表动态的都不对.