How can you determine the past arrangement of leaves on a bare twig?

The determination of the past arrangement of leaves from bare twig  are

Explanation:

Terminal bud:  it is the large bud at the apex of the twig.  Uses of the bud is to protect the dormant meristem.  

Bud scale: a small modified leaf on outside of bud.

Auxiliary bud: It is found just above the each leaf scar. Not all twig will have a full complementary of auxiliary buds. They frequently gets damaged.

Lenticles: Opening in the bark that allows for gas exchange into and out of underlying living tissues.  

Leaf scars: It is present at  the stem for the triangular regions.

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.