A:①②
B:②③
C:③④
D:①③
This book is old, b____I like it a lot.
The young lady ____(表现) courageously in the face of danger.
将某植物放置在黑暗处一昼夜后,选取一叶片按图甲处理,照光几小时后,摘下叶片,去掉锡箔,经脱色、漂洗再碘液处理,结果如图乙所示.下列分析中错误的是( )
下列能够聚合成DNA分子的物质是