Although Virginia is entitled to five personal and dependency exemptions on her income tax return, she claims

Question:

Although Virginia is entitled to five personal and dependency exemptions on her income tax return, she claims only one withholding allowance on Form W-4.
a. Is it permissible to claim fewer allowances than an individual is entitled to?
b. Why would an individual claim fewer allowances?
c. Is it possible for Virginia to claim more than five withholding allowances?