题目 :在相同光照和温度条件下 ,空气中CO2 含量与植物光合产量 (有机物积累量 )的关系如图 1所示。理论上某种C3 植物能更有效地利用CO2 ,使光合产量高于m点的选项是 (　　 )图 1A .若a点在a2 ,b点在b2 时B .若a点在a1,b点在b1时C .若a点在a2 ,b点在b1时D .若a点在a1,b点在b2 Title : The relationship between CO2 content in air and photosynthetic yield (organic accumulation) of plants under the same light and temperature conditions is shown in Figure 1. In theory, some C3 plants can use CO2 more efficiently, and the option for photosynthetic yields higher than m points is (Figure 1A). If a is at a2 and b is at b2, B is at a1, b is at When b1 is C, if a is at a2, b is at b1 D. If a is at a1, b is at b2