Which of the Following Statements Regarding a Taxpayer's Principal Residence

Which of the following statements regarding a taxpayer's principal residence is true for 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 these statements is true.