先秦道家的代表人物是()和(),道家主张()。
参考答案:老子、庄子、无为而治
—Did you go to Ann's birthday party?
—No, I __________. [ ]
A. didn't invite
B. wasn't inviting
C. hadn't invited
D. wasn't invited
生物量是指在任一时间里实际测得的单位面积内有机物总量,一般用______来表示。