Answer
C.
Work Step by Step
The AP axis is such a critical aspect of development in Drosophila that its loss would lead to catastrophic problems for the embryo, which would die (C.) A. and B. are both wrong since such a loss would affect both embryo and adult, if the latter even appeared, and D. is incorrect since the kind of change it describes is homeosis, which occurs with much later-acting genes which have much less severe effects.