Because uranium is the heaviest, and it is therefore the most penetrating, of natural metals, it is being increasingly used in the production of armor-piercing bullets and rockets.
A) and it is therefore the most penetrating, of natural metals, it is being increasingly used
B) and it is therefore the most penetrating of natural metals, it has increased use
C) and therefore the most penetrating, of natural metals, it is being increasingly used
D) and therefore it is the most penetrating of natural metals, it is increasingly used
E) therefore the most penetrating, of natural metals it is being increasingly used