A:lies a very deep valley
B:does a very deep valley lie
C:a very deep valley lie
D:a very deep valley lay
—Are Lucy and Lily having lunch at school now?
—__________.
现有AaBB和AAbb两种基因型的豌豆植株,假设这两种基因型植株的数量和它们的生殖能力均相同,在自然状态下,子一代中能稳定遗传的个体所占比例是()