问答题 What may make  the international sale of goods more complex than the domestic sale? A、Different language B、Different culture C、Different currency D、Long distance of transport E、Different legal system F、Different metrology system

单项选择题 有关杂种优势，论述不正确的是：（ ）

判断题 绝对致死量或绝对致死浓度(LD100或LC100)指药物能引起一群实验动物50%死亡的剂量或浓度。