An Anticline fold may be defined as fold that

An anticline fold is a type of geological fold that has the following characteristics:

Convex upward: The fold arches upward, forming a convex shape when viewed in cross-section. Hence, Option A is correct.

Older rocks in centre: Due to the upward arching, the oldest rock layers are exposed in the central part of the anticline, with progressively younger rocks towards the limbs. Hence, Option B is correct.

Two limbs dip away from each other: In an anticline, the limbs slope away from the crest of the fold. Hence, Option C is correct.

Since all three conditions are true for an anticline fold, the correct answer is Option D: All of these.