Indicate whether the following statements are "True" or "False" regarding the "Statements on Standards for Tax Services" dealing with CPAs engaged in tax practice.

a$.$ Although these pronouncements are part of the AICPA's Code of Professional Conduct, they are not enforceable.

b$.$ Any tax position taken should be supported by a good$-$faith belief that they have a realistic possibility of being sustained, if challenged.

c$.$ A practitioner can never use a client's estimates.

d$.$ Every effort should be made to answer questions appearing on tax returns.