The Sun is approximately 5 million km further from the Southern Hemisphere during their winter than it is to North America during our winter. Because of the precession of the Earth's axis, this will change in about 14,000 years or so - the Earth will then be much further from the Sun during our winter. Global warming might be welcomed with open arms then. But the distance to the Sun is not as important as the tilt of the Earth's axis, elevation above sea level, or proximity to polar land masses in affecting whether or not snow is likely to be a common feature of the winter landscape.

In the Southern Hemisphere, ocean water moderates the influence of the cold air pulsing northward from Antarctica. However, in the Northern Hemisphere, the land masses are situated closer to the poles, which not only act as source areas for cold air, but because of its lower thermal inertia compared to water, the land does not modify the cold temperatures nearly as much as does water, even cold water. The end result is that the middle latitudes are much cooler during winter in the Northern Hemisphere than in the Southern Hemisphere.

Associated with this is the fact that high pressure systems or anticyclones occur less frequently in the Southern Hemisphere than in the Northern Hemisphere. Because there's less land in the mid latitudes of the Southern Hemisphere, the southern westerlies are stronger than their northern counterpart, and large nearly stationary "high" systems such as the "Siberian High" have a harder time becoming established. These large "highs" are important in refrigerating air and determining the tracks of storm systems.

Despite these drawbacks, snow does occur in the middle latitudes of the Southern Hemisphere and occasionally even in the sub-tropics. It can snow in South Africa, about as often as in southern Florida, but it certainly doesn't snow during there summer (December-February), so the statement C is false. In Australia, as is the case in South Africa, snow is a novelty. Melbourne, for instance, records a snowfall only a few times each century. However, in the Snowy Mountains of southeastern Australia, snow falls each year, and a snowpack several meters in depth has been observed in some years. New Zealand, due to its more southerly (poleward) location and higher average elevation compared to Australia, has a greater snow cover despite its much smaller size. Snow can occur at elevations as low as about 1,000 meters on the North Island in winter, but on the South Island, snow can occur in the Southern Alps at any time of year. Mt Cook, the highest peak in the Southern Alps, is about 3,700 meters above sea level. Even coastal cities such as Christchurch, about the same latitude as Portland, Maine, can maintain a covering of snow for several days in succession during the winter months.

South America is the only continent in the Southern Hemisphere (other than Antarctica) where an extensive, non mountainous, winter snow cover may occur. So A is false too - perhaps you're able to guess the correct answer now). In southern Argentina, snow may accumulate as early as May and as late as October. Each winter, snow is a regular feature south of about 45 degrees latitude, and in the snowiest years, over 1 million square km of snow has been measured - about the size of Montana, Wyoming, Colorado, and Utah combined.