一个自然种群中,假设由基因型为AA、Aa和aa的个体组成,其中AA占30%,aa占20%,则该种群中a的基因频率为( )
A:30%
B:45%
C:50%
D:55%
根据拼音写词语。
miàn duì
jiāng lái
yè jiān
míng lǎng
zhèn yǔ
____
如图,△ABC∽△AED,∠ADE=80°,∠A=60°,则∠B等于( )
在分层设色地形图上,高原一般用什么颜色表示( )
A. carrots B. milk C. sandwich D. beef E. delicious
Hi, I' m Mary. My favourite food is a ____. It's ____.I don't like____but chicken is OK. My favourite vegetables are ____.I like ____very much.
下列行为属于正确行使公民权利的是 ( )