The answer is: C. Beautiful and pleasing
In this poem the speaker uses the similes, a simile is the competition within two object in order to give the reading a more detail view of what is being described, in this case Burns compare his beloved with a rose and a sweet-sounding melody, then we can analyze which qualities has each one of those. The rose is beautiful and fresh then a sweet-sounding melody can be delightful to listen or pleasant to hear.