Which of the following is NOT a potential risk of relying on sales taxes as a principal source of revenue? a) The productivity of the tax is threatened by the increase in purchases through remote venders (e.g., phone, mail order, internet, etc.). b) There is a trend toward the purchase of more services and fewer goods that can lead to losses in revenues. c) Sales taxes decrease consumer purchases and lead to losses of revenues. d) Legislatures have caused revenue losses by declaring exemptions like tax holidays to spur more shopping. e) They are all potential risks.