Which statement about romanticism in the arts is true?
a. romantic art adopted the neoclassical traits of order and balance.
b. romantic art captured the power and beauty of nature on canvas.
c. romantic art appealed to the viewer's reason and the intellect.
d. romantic art used strict rules for form and content.

That would be:

b. Romantic art captured the power and beauty of nature on canvas.
Neoclassical art characteristics are about deduction and human beings and paid attention technicalities of literary such as diction and grammar.

This definition fits letters a, c and d.

 One of the Romantic period’s characteristics was the expression of strong senses, emotions, and feelings in literary, art and music. Romantics rejected the idea of deduction – the process of gaining knowledge by using logic or reason; rather, they believe that it is gained through intuition, the ‘gut feeling’ – knowing something through natural feeling as guidance without evidence. In turn, this period emphasizes more on exaggerated emotions of awe, apprehension, horror and terror which intensifies the subjective perspective of one’s experiences.

These definitions fit letter b.