A.The Titanic on April 15, 1912, hit an iceberg and sank even though it was considered unsinkable
Jason is correct, you need a comma after the word "sank".
In addition, the word order is not good.
"on April 15, 1912" is not in the correct place.
The normal word order in English is:
Subject - verb - object - place - manner - time
The Titanic (s) hit (v) and iceberg (o) on April 15, 1912.
In your sentence, because you have additional information, I would say:
On April 15, 1912, the Titanic, considered an 'unsinkable ship', hit an iceberg in the Atlantic Ocean, and sank.