A:C2H6O2
B:CH4和C2H6的混合物
C:CH4O和C3H8O的混合物
D:C2H6O和C3H8O3的混合物
对光完成的标志是要看到明亮的圆形视野.(判断对错)
He always sits the classroom, because he is short(矮).