A. The pressure is lower as you gain altitude because there are more molecules of oxygen and nitrogen. B. The pressure is lower as you gain altitude because there are less molecules of oxygen and nitrogen. C. The pressure is the same because there is no change in the number of molecules.
The price of a cockatiel depends on a few factors. Firstly the price depends on whether or not the bird is tamed. For a tamed cockatiel it would cost around $80 - $120 and a untamed cockatiel would cost $15-$30 (AUS) Also the colouring of the cockatiel plays a part in the cost of the bird, as more rare colours (such as lutino or pearl cinnamon) may increase the cost of the cockatiel.
Since there are so many varieties, the price can be all over the place. For instance, a Normal Grey Cockatiel can retail for $60 to $80, while a Cinnamon Cockatiel can range from $75 to $95. Higher-end Albino Cockatiels, for example, can cost as much as $140. On BirdsNow.com, an online bird classified website, has more than 500 listings at the time of this writing. Most of the prices, from what we researched, were anywhere from $70 to $350+ These birds can often be found at a big box pet stores such as Petsmart and Petco.