Vivaldi was famous and influential as a virtuosoa. harpsichordist. b. opera singer. c. lutenist. d. violinist.

D. violinist.

Explanation:

Antonio Lucio Vivaldi was known as a violin virtuoso, one of the greatest players of his time.  His  father taught him how to play violin.

He began his rich musical career as a violinist, then was a teacher.  He composed a few pieces before publishing his first major piece as a composer.

He wrote many types of music: instrumental, lyric and even religious one, since he was also a Catholic priest.

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.