A:均发生于有丝分裂的间期
B:a发生于有丝分裂的间期,b发生于减数第一次分裂前的间期
C:均发生于减数第一次分裂前的间期
D:a发生于有丝分裂间期,b发生于减数第二次分裂前的间期
家庭轿车的大量使用可能引发的环境问题是( )
阅读下面的古文选段,完成小题。 孟子曰:“虽有天下易生之物也,一日暴之,十日寒之,未有能生者也。吾见亦罕矣,吾退而寒之者至矣,吾如有萌焉何哉?今夫弈之为数,小数也;不专心致志,则不得也。弈秋,通国之善弈者也。使弈秋诲二人弈:其一人专心致志,惟弈秋之为听;一人虽听之,一心以为有鸿鹄将至,思援弓缴而射之,虽与之俱学,弗若之矣。为是其智弗若与?曰:非然也。” (《孟子·告子上》)
当土壤中含____ 过多,超过土壤的____能力时,就会引起土壤的 ____、 ____和功能方式变化,微生物活动受到抑制,有害物质或其分解产物在土壤中逐渐____,间接被人体____,达到危害人体健康的程度,就是土壤污染。
当今的爬行动物不可能进化成鸟类和哺乳类。( )
My name is Chen Lan. My home is in Gulangyu. Do you know it? It is in Xiamen. It is near the sea(海). Gulangyu is a small place,but it is very nice and clean. There are no cars,no buses. People only walk. So it is very quiet. Our house is in the middle of Gulangyu. Behind our house there is a big old tree. My grandfather tells me that the tree is very,very old. There are many birds in the tree. We call it a “bird tree”. Our house is near the sea. The sea is big and blue. There are a lot of fish in the sea. After school,I go there and catch(捉) fish with my friends. It is very interesting. I like fish and I like catching fish.