請回答18到21：When C. J. Liu bills her clients, all it takes is a few mouse clicks, and for the most part their payments end up in her bank account a few days later. She does not need an assistant to send out receipts or to track accounts payable and receivable. She never has to wait for checks to arrive in the mail, and she does not have to visit the bank. Like many others who run small businesses, Ms. Liu is a PayPal customer.From its inception seven years ago, PayPal, based in San Jose, Calif., has grown to service more than 86.6 million accounts in 55 countries, and it expects to process $25 billion in money transfers this year. About 70 percent of the payment volume comes through PayPal’s parent company, eBay, and is used to buy and sell items on the Internet. But more and more, small businesses and sole proprietors outside of eBay are using PayPal as their back offices.Based on her business volume, less than $3,000 a month, Ms. Liu pays 2.8 percent of her total sales, as well as 30 cents a transaction, for this service. “It saves me the hassle of the billing side,” she said, “so I can concentrate on my client work.”Many of the newest and smallest businesses find that using PayPal is more cost-effective than turning directly to a credit card company to process transactions. “PayPal is building their fortune on the small businesses that credit card companies wouldn’t take unless they paid 7 to 12 percent of every transaction,” she said.43 What is this article mainly about?
(A) The commercial advantage of eBay.
(B) The success of a Chinese business woman.
(C) The convenience of PayPal for small businesses.
(D) The birth of a new product of eBay.