Answer:
Since the middle of the 20th century, scientists <u>have found</u> cures for many diseases. However, so far no one <u>has discovered</u>
Explanation:
those are the perfect tenses for (find) and (discover)
Omniscient narrator should be the answer.
I think the answer is number 1! Hope this helps! :)
A. Side a is 175 inches long, side b is 150 inches long, and side c is 75 inches long.
(i think)