Do Anticlines form under extension or compression?

Question

Particularly, the example in question is an Upright fold rather than a plunging fold

Answer 1

Let's make sure you know the terminology:

1. Anticline: an arch-like shaped bend in crust
2. Extension: a fault where plates move apart
3. Compression: a fault where plates are pushed together

Knowing these key words the the answer becomes obvious it is compression.

Real World Example:

Take a piece of paper and puts your hands on either side of it. When your hands move apart (extension) the paper rips. When your hands move together the paper folds into an arch.