图甲是生态系统中碳循环示意图，图中“→”表示碳元素的流动方向。
碳元素在生物群落和无机环境之间的循环主要是以（）形式进行的。
参考答案：
CO2
A: I had a great time ______ games with my friends in the park yesterday.
B: How great! But I didn’t have any time _______ at all, I had to get ready for the test.
A．playing; to play
B．play; to play
C．playing; playing
D．to play; playing
石材饰面工程中，小规格饰面板边长小于0、4米，安装高度（）。
A、不超过5M
B、不超过3M
C、不超过2M
D、不超过1M
