Adding copper or magnesium to aluminum creates an alloy that is more flammable than magnesium heavier than steel stronger than aluminum

stronger than aluminum

The given blank can be filled with stronger than aluminium.

Explanation:

The metals, which have been mixed with other elements or metals to obtain new characteristics are known as alloys. The metal alloys generally provide more durability, greater strength, and flexibility over the base metal. One of the prime advantages of a metal alloy is that it can strengthen metal or can minimize cost, and at the same time sustaining some of its own substantial characteristics.  

In aluminum alloys, aluminum is the main metal amalgamated with magnesium, zinc, copper, or other metals.  

first one is the correct answer