Which of these describes a trait under incomplete dominance?

In the context of incomplete dominance, the key feature is that neither allele is completely dominant over the other, which results in a blending of traits in the phenotype. For instance, if you have a flower where one parent has red petals and the other has white petals, the offspring may exhibit pink petals, demonstrating that the red and white traits mix rather than one being dominant and completely masking the other.

This blending phenomenon distinguishes incomplete dominance from complete dominance, where one allele's trait would completely overshadow the other. In incomplete dominance, the resultant phenotype reflects a mixture of both alleles rather than the expression of just one, which is why the correct description is that the traits blend in the phenotype.