A sighn that evidence is strong is if it comes from a(n)source.​

A sign that evidence is strong is if it comes from a(n) firsthand source..

the printing press made a huge difference in the arts and crafts movement.

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.