Your A) SAVINGS should furnish enough money to live on, in an emergency, for six months.
Savings should at minimum be equivalent to the amount you spend for your basic needs for a month. Multiply it for 6 months because in case you are unemployed, you will still be able to meet your needs for six months. Giving you time to recoup and find other employment.
IRA is Individual Retirement Account - This is intended for your retirement.
Investments are usually bonds or securities which may take quite some time before it can be liquidated.