It's hot this summer. ________, it was ________ hotter last summer.
A:However; very
B:Although; very
C:However, even
D:Although; even
要使马铃薯和甘薯高产应当注意使用哪种无机盐( )
观察方框中的分子模型,并判断下列说法错误的是(一种圆圈代表一种原子)( )
在动物的进化历程中,最早成为真正陆生脊椎动物的是( )