Read the thesis sentence.

music classes are an important part of a complete education.

which topic sentence does not support a unified composition?

music can convey ideas in ways that literature cannot.

our school orchestra performs regularly at school events.

music is a key element in cultures throughout history.

the study of music increases performance in math and science.

I would say the correct answer is - Our school orchestra performs regularly at school events.

comfortable

explanation:

one type of the adjectives is predicate adjective. a predicate adjective is an adjective which follows a linking verb and modifies or refers back to the main subject of that linking verb.

it usually is used just before the noun it modies.

here in this example:

'penguins seem comfortable in the coolest habitats', comfortable is the predicate adjective which follows the linking verb 'seem' and modifies the noun.