Transcendentalism a subgenre of american romanticism was based in which

Natural and spiritual world are connected.

Explanation:

Transcendentalism was an American philosophical movement developed during the late 1820s and early 1830s. The originator of this philosophy is considered Ralph Waldo Emerson. The thinkers of this movement adopted the ideas of Immanuel Kant, Samuel Taylor Coleridge, and also referred to ancient Indian texts such as Vedas.

The thinkers and practitioners of this belief believed that the natural world and the spiritual world are connected. They adopted the idea and beliefs of idealism also that focused on nature. They sternly opposed materialism.

So, the correct answer is that they believed that the natural and spiritual worlds are connected.