Which word could best replace either the underlined phrase or word in the paragraph?

i’ve been volunteering for a dog rescue group and was asked to speak at a charity event. at first i said i would be glad to do it, but on the night of the event, i started to get butterflies in my stomach. as i practiced my speech, i got even more nervous. once i began speaking though, i became more relaxed.

a.
troubled

b.
comfortable

c.
sick

d.
anxious