正确答案: C

杂交时，须在开花前除去母本的雌蕊

题目：扩豌豆进行遗传试验时，下列操作错误的是

解析：

豌豆为雌雄同株，自花授粉且是闭花授粉，自然状态下都是自交，孟德尔的豌豆杂交实验是人工杂交，在花蕾期人工去雄。

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举一反三的答案和解析：

[单选题]藻类植物都是单细胞或多细胞。( )

错误

[单选题]CAlex London Research Laboratory (ALRL) is part of Alex Co., Ltd., a major Australian medicine-making company. Opened in 1992, ALRL specialises in the development of new medicines for the treatment of heart diseases．

They have not yet been set up．

[单选题]根据下面内容，回答 68~71题：DIt’s not easy being a teenager(13至19岁青少年)-nor is it easy being the parent of a teenager．You can make your child feel angry, hurt or misunderstood by what you say without realizing it yourself．It is important to give your child the space he needs to grow while gently letting him know that you’11 still be there for him when he needs you．Expect a lot from your child，just not everything．Except for health and safety problems， such as drug use or careless driving，consider everything else open to discussion．If your child is unwilling to discuss something，don’t insist he tell you what’s on his mind．The more you insist， the more likely that he’11 clam up．Instead，let him attempt to solve(解决)things by himself. At the same time，remind him that you’re always there for him should he seek advice or help．Show respect for your teenager’s privacy(隐私)．Never read his mail or listen in on personal conversations．

how to help a teenager grow up

[单选题]下列几组词汇，最能准确反映“过渡时期”这一特殊年代的是

工业化 抗美援朝 三大改造

[单选题]蔷薇科(Rosaceae)根据果实的不同分为4个亚科。( )

正确

[单选题]垂周分裂所形成的新细胞壁和器官表面垂直。( )

正确