A:an underground lake was discovered
B:workers discovered an underground lake
C:there was an underground lake discovered
D:a lake was discovered underground
初至天目双清庄记
数日阴雨,苦甚。至双清庄,天稍霁。
庄在山脚,诸僧留宿庄中。僧房甚精,溪流激石作声,彻夜到枕上。石篑梦中误以为雨,愁极,遂不能寐。
次早,山僧供茗糜,邀石篑起。石篑叹日: “暴雨如此,将安归乎?有卧游耳。”僧日:“天已晴,风日甚美,响者乃溪声,非雨声也。”
石篑大笑,急披衣起,啜茗数碗,即同行。
12-4=____
7-3=____
13-5=____
8+7=____
8-7=____