T/f all metals have two oxidation numbers

False

Explanation:

The metals of the 1A and 2A group has only 1 oxidation number.

In 1A metals have oxidation number +1, in 2A  oxidation number of metals is +2. Al has "+3".

Other metals like Mn have several oxidation numbers +2,+3,+4,+6,+7.

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.