lǎo / shī / ràng / wǒ / men / bǐ / jiào / jiǎn / tǔ / jīn / shǔ / hé / jiǎn / jīn / shǔ / de / xìng / zhì老师让我们比较碱土金属和碱金属的性质。The teacher asked us to compare the properties of alkaline earth metals and alkali metals.