Air mass, letter a is the correct one
Earth’s atmosphere is a mixture of nitrogen (79%), oxygen (20%), and a small fraction of carbon dioxide, water vapours and other gases. This makes the existence of life possible on Earth. However, the atmospheres on Venus and Mars mainly consist of carbon dioxide. The amount of carbon dioxide on these planets can range from 95% to 97%. This may be the reason no life exists on these planets.
The atmosphere of Venus is about 96 per cent carbon dioxide, with surface temperatures around 737 K (464 °C, or 867 °F).
Venus itself rotates only once every 243 Earth days.
Mars, in contrast, has a thin atmosphere composed of about 95 per cent carbon dioxide, with the remainder being mostly diatomic nitrogen.
That's a "Tropical Storm".
It's not a "hurricane" until winds are up around 100 km/hr.
The distance between the east coast and west coast of Australia is 2,500 mi.
Australia is an island country that is also a continent on its own, and that makes it unique. It is one of the biggest countries in the world, and no wonder that it is a very long and wide country.
In a straight line, Australia's east coast is 2,500 mi away from the west coast of the country.
The biggest and most influential city in the east coast is Brisbane, while on the west coast it is Perth that has that role.
