liàng shài
xiǎo xiàng
zhuàn qián
chān jiǎ
yāo qǐng
____
His parents didn't earn much money so he dropped out of school because of p____(贫穷).
①水 ②石油 ③森林 ④土地 ⑤铁矿 ⑥太阳能 ⑦煤
的终边上一点P（
，
），则
等于（ ）