单项选择题
A．at the beginning of the nineteenth century B．in the middle of the nineteenth century C．more than two hundred years ago D．when people first sent letters and postcards.
A．How did stamps begin t6 be used B．Why were postmen sent to get postage C．When did people first begin to use stamps D．Who was the first to think of using stamps
A．was paid by the letter-writers B．was paid by the letter-receivers C．was got by postmen D．both B and C