元素
O
C
H
N
P
S
占细胞干重的百分比(%)
14.62
55.99
7.46
9.33
3.11
0.78
占细胞鲜重的百分比(%)
65.0
18.0
10.0
3.0
1.40
0.30
用反证法证明命题:“三角形的内角中至少有一个不大于60度”时,反设正确的是( )
仿照例子写句子。
例子:I watched TV last night. And you?
Did you watch TV last night?