According to ABCDE model, ovule identity is specified by:
C + D + E (C) is correct here. This is core ABCE & ABCDE MODEL +Synapdrgon flowering: once you know the definition or pathway step, C + D + E is the clear fit. The wrong ones are A) A + B; B) B + C; D) D + E. If the topic is about gradients or potentials, water/solutes move from higher to lower of the relevant quantity.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.