The other parents tried to pull the heartbroken father off was left of the school,saying “It's too late to dig! They are all dead.” A.that B.what C.which D.where 答案:B
科学家从烟草花叶病毒(TMV)中分离出a、b两个不同品系,它们感染植物产生的病斑形态不同。下列4组实验(见下表)中,不可能出现的结果是
A.
实验①
B.
实验②
C.
实验③
D.
实验④