A:①②③
B:①②④
C:②③④
D:①③④
用基因型为DdTt的植株所产生的花粉粒,经分别离体培养成幼苗,再用秋水仙素处理,使其成为二倍体,这些幼苗长成后的自交后代( )
Many students take the school bus to school every day. Parents think taking the school bus is usually safe (安全的), but sometimes it is dangerous. Some students don't keep the school bus rules. What are the school bus rules?
Arrive at the bus station early.
Wait for (等候) the school bus at the bus station.
Don't run at the bus station.
Don't walk or fight on the bus.
Don't get off (下车) the bus when it goes.
古今中外,无数的智者为我们点亮一盏盏智慧之灯。让我们一起开始走进他们的世界,领略他们留下的文化魅力。【孔庙朝圣】杏坛(山东曲阜孔庙) 大成殿匾额(北京孔庙)【老书探密】(2)【静坐沉思】