Indicate whether the following statements are "True" or "False" regarding the statute of limitations.

a.	If no return is filed or a fraudulent return is filed, assessments can be made at any time.
b.	If a taxpayer omits an amount of gross income in excess of 25 percent of the gross income stated on the return, the statute of limitations does not apply.
c.	In general, any tax that is imposed must be assessed within three years of the later of (a) the filing date of the return or (b) the unextended due date of the return.
d.	The statute of limitations may be extended for a fixed period of time by mutual consent of the IRS and the taxpayer.