In: Economics
a) The government sends out social security checks to some households: The given transaction will not be included in the GDP because the GDP doesn't include transfer payments. All the social security are apart of transfer payments i.e. nothing is given back in return for social security.
b) People painting their own house will be an unpaid work which will not be included in the GDP. If the same work is done by some person hired and paid for the same work then it will be included in the GDP but unpaid works like household chores and doing unpaid works is not included in the GDP.
c) Stocks are not included in the GDP. GD include the things which result in some value addition or is related to something new created. A stock is just equity changing hands and not new creating or value addition.
d) Yes, the fee of the financial brokers is included in the GDP. The fees received by the financial broker are the part of income earned by them in exchange for their services.