Cotton--nice and soft.

选D
feel在这里是作系动词,意为“摸起来.”
类似的表感官的系动词还有：look 看起来.,taste 尝起来.,smell 闻起来.,sound 听起来.
它们都没有进行时态和被动语态
Your idea sounds reasonable.
The dish tastes nice.
The shirt smells terrible.
The flower looks beautiful.