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.
Cockatiels reach adult size at about 8 weeks of age. Males are typically 12-13 inches long (30-33cm) and weigh 2 5/8 to 3 2/3 ounces (80 - 102 grams) Females are the same in lenght but typically weigh a little less than males. They are native to Austrailia and in captivity live about 20 years.