A. Anatropous ovule is the most common type of ovules, occurring in more than 80% angiospermic families. The body of ovule is rotated by 180° and micropyle comes near to the funiculus. Chalaza and micropyle are in straight line but hilum is 90° to micropyle.
B. In Amphitropous ovule, the body of ovule becomes curved and looks like the anatropous ovule but embryo sac also curves and becomes horse-shoe shaped.
C. In Campylotropous ovule, the curvature is such that the micropyle comes to lie near the funiculus.
D. Orthotropous ovule is the simplest and primitive type of ovule in which micropyle, chalaza and funiculus lie in one vertical plane.
Hence when the hilum, chalaza and micropyle of the ovule lie in the same longitudinal axis, it is known as Orthotropous ovule.
So, the correct answer is 'Orthotropous ovule'.