The romantic period of music was known for

A vibrant and unexpected key changes
B little use of dynamic Changes
C few notable composers
D minimal sense of storytelling

A vibrant and unexpected key changes.

Romantic music is a stylistic movement in Western Classical music associated with the period of the 19th century commonly referred to as the Romantic era (or Romantic period). It is closely related to the broader concept of Romanticism—the intellectual, artistic and literary movement that became prominent in Western culture from approximately 1798 until 1837.[1]

Romantic composers sought to create music that was individualistic, emotional, dramatic and often programmatic; reflecting broader trends within the movements of Romantic literature, poetry, art, and philosophy. Romantic music was often ostensibly inspired by (or else sought to evoke) non-musical stimuli, such as nature, literature, poetry, super-natural elements or the fine arts. It included features such as increased chromaticism and moved away from traditional forms.[2]

Background
Main article: Romanticism
Further information: Transition from Classical to Romantic music

Wanderer above the Sea of Fog, by Caspar David Friedrich, is an example of Romantic painting.
The Romantic movement was an artistic, literary, and intellectual movement that originated in the second half of the 18th century in Europe and strengthened in reaction to the Industrial Revolution.[3] In part, it was a revolt against social and political norms of the Age of Enlightenment and a reaction against the scientific rationalization of nature (Casey 2008). It was embodied most strongly in the visual arts, music, literature,[4] and education,[5] and was in turn influenced by developments in natural history.[6]

One of the first significant applications of the term to music was in 1789, in the Mémoires by the Frenchman André Grétry, but it was E. T. A. Hoffmann who established the principles of musical romanticism, in a lengthy review of Ludwig van Beethoven's Fifth Symphony published in 1810, and an 1813 article on Beethoven's instrumental music. In the first of these essays Hoffmann traced the beginnings of musical Romanticism to the later works of Haydn and Mozart. It was Hoffmann's fusion of ideas already associated with the term "Romantic", used in opposition to the restraint and formality of Classical models, that elevated music, and especially instrumental music, to a position of pre-eminence in Romanticism as the art most suited to the expression of emotions. It was also through the writings of Hoffmann and other German authors that German music was brought to the center of musical Romanticism.[7]

The Romantic movement in music was characterized by an emphasis on individualism, emotion, drama, and programmatic elements, as well as a move away from traditional forms and increased chromaticism. It was part of a broader cultural movement of Romanticism, which originated as a reaction against social and political norms of the Enlightenment and the scientific rationalization of nature. E.T.A. Hoffmann was one of the key writers who established the principles of musical Romanticism, elevating music and instrumental music as the art best suited for the expression of emotions. German music was brought to the forefront of this movement through the writings of Hoffmann and other authors.

The correct answer is A, vibrant and unexpected key changes.

To arrive at this answer, you can start by understanding what the romantic period of music is. The romantic period occurred in Western classical music from the late 18th to the early 19th century and was characterized by an emphasis on emotional expression, individualism, and imagination.

Next, you can eliminate options C and D, as they are clearly incorrect. The romantic period had many notable composers, such as Ludwig van Beethoven, Franz Schubert, Frederic Chopin, and Richard Wagner. Additionally, storytelling was an essential element of romantic music, with composers often trying to convey narratives or emotions through their compositions.

This leaves us with options A and B. To determine the correct answer, you need to consider the defining characteristics of the romantic period. While dynamic changes (the variation of volume or intensity in music) were indeed significant during this period, they were not minimized or neglected. In fact, composers during the romantic period frequently utilized dynamic changes to evoke different emotions and create dramatic effects.

That leaves us with option A, vibrant and unexpected key changes. This characteristic was indeed prominent in romantic music. Composers of this period often employed modulation, which is the process of changing from one key to another, to add richness, excitement, and unpredictability to their compositions. These key changes were often sudden and unexpected, bringing about new tonal colors and emotional depths to the music.

Hence, the romantic period of music was known for vibrant and unexpected key changes.