读单词,圈出划线部分发音不同于其他三个的词。
He lived ________ a big cave. A.inB.onC.at
Peking Man lived about 300,000 ________ 500,000 years ago. A.from B.toC.for
What's your mother's ________? A.work B.do C.job
What class are you ________? A.at B.in C.on
How old ________ your brother? A.is B.are C.does