What do scientists consider air, temperature ans water to be in the environment

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

May someone me with these science questions

You open a can of soda at room temperature and hear a hiss. which of the following factors has changed inside the container? a.) atmospheric pressure b.) temperature of gas c.) type of gas d.) amount of gas