What happens when the south end of earth's axis is tilted toward the sun ?

Summer in the southern hemisphere.

Explanation:

As the earth axis is based on a 23.4 ° the rotational motion and the distance of the earth from the sun exerts a dynamic influence on the north and the southern sides.  Thus the northern hemisphere has a winter season when the earth is tilted more towards the sun and the southern landmass experiences the summers as the earth has more direct rays of the sun in that part as compared to the summers in the northern hemisphere.  Hence the southern end celebrates Christmas when it summers in the north as they have the contrasting seasonal reversals.

It is c. naturally in the environment

Answer the use of flood plains and irrigation;