The most active metals on the periodic table are found on the: lower left upper right middle upper left lower right

The correct answer is lower left.

Explanation:

Metals are defined as the elements which loose electrons to attain stable electronic configuration.

Reactivity of metals is defined as the tendency of metals to loose electrons. If a metal looses electrons easily, it means that it is more reactive.

Reactivity increases down the group and decreases across a period for metals.

In the periodic table attached,

The elements present in lower left are metals which are most reactive.The elements present in upper right are non-metals which are most reactive.The elements present in middle are metals which are less reactive.The elements present in upper left are metals which are least reactive reactive.The elements present in lower right are non-metals which are least reactive.

Hence, the correct answer is lower left.

D)can be increased in a closed system

The answer is d.potassium