Which of the following statements regarding a taxpayer's principal residence is true for the purposes of determining whether the taxpayer is eligible to exclude gain realized on the sale of the residence?
a) a taxpayer may have more than one principal residence at any one time. b) a taxpayer's principal residence may not be a houseboat. c) a taxpayer with more than one residence may annually elect which residence is considered to be the principal residence. d) none of the choices are true.