Which of the following will increase the demand for burgers, a normal good? 
选项为:A:An increase in consumers\textquotesingle{} income  B:A decrease in the price of burgers  C:An increase in the cost of beef used in producing burgers  D:An increase in the number of restaurants selling burgers  E:An increase in the price of a complementary product  请回答其中一个选项.