Answer:
Easygoing
Explanation:
The only adjective in the given sentence is<em> easygoing</em> (= <em>relaxed and casual in style or manner</em>).
<em>The</em> is a definite article.
<em>Astronauts</em> is a noun.
<em>Were</em> is a verb.
<em>Not</em> is an adverb.
<em>Like</em> is a conjunction.
<em>Supergirl</em> is a noun.
<em>Was</em> is a verb.
