Four common investments include all of these, except real estate stock mutual fund junk bonds retirement accounts

All of the choices are examples of investment except retirement accounts. This is a misconception of many. Retirement accounts are not an investment. It is only an account. It is basically a savings account for your retirement with tax-free growth.

No, because there could be bacteria in the solution 

Answertotal amount of additional increases in consumption spending induced by an initial change in aggregate expenditure;