Close Meaning

Which is correct?

" It was not until 1761 that navigators could discover their exact longitude at sea."

A- The year 1761 has no special meaning for navigators in terms of discovering their exact longitude at sea

B- After 1761, it became less important to be able to discover one's exact longitude at sea

C- Before 1761, it was hard and costly for navigators to discover their exact longitude at sea

D- Navigators waited until 1761 to announce their exact longtitude at sea

E- In 1761, it became possible for navigators to discover their exact longitude at sea

My answer is E.