光补偿点
参考答案：
植物光合作用吸收的CO2量与呼吸排放的CO2量相等时的最低光照强度为植物的光补偿点。
It is a pity that none of the ______ stopped ______ the poor man lying there, begging. [ ]
A. passer-bys; to help
B. passers-by; helping
C. passer-bys; helping
D. passers-by; to help
咳嗽伴咯血常见于
A．肺气肿
B．肺脓肿
C．支气管扩张
D．肺结核
E．二尖瓣狭窄
