问题
选择题
| By the time he arrives in Beijing, we________ here for two days. |
A. will have stayed |
答案
答案：A
搜题请搜索小程序“爱下问搜题”
| By the time he arrives in Beijing, we________ here for two days. |
A. will have stayed |
答案：A
铅是一种在生物体内难以分解和排出的物质．在一个受铅污染的生态系统中，发现有甲、乙、丙、丁四种生物之间存在吃与被吃的关系，经检测它们体内残留的铅含量情况如表，那么四种生物之间最可能的食物链构成是（ ）
| 生物 | 甲 | 乙 | 丙 | 丁 |
| 铅的相对含量 | 0.04 | 6.00 | 0.49 | 61.00 |
A．乙→丙→丁→甲 B．丁→乙→丙→甲
C．甲→丙→乙→丁 D．甲→乙→丙→丁