A：表皮
B：气孔
C：叶肉
D：叶脉
穿过英国伦敦格林尼治天文台旧址的经线是（ ）
A.长方形 B.圆形 C.正方形
The book was written in _______ easy English _______ even primary school students could understand it.
一条染色体上含有不止一个基因．（判断对错）
