一名45 歲女性，最近幾個月來常覺得胃液逆流及燒灼感。接受胃鏡檢查。圖示是食道組織切片顯微鏡下變化。下列何種過程最可以解釋此種變化？
Apoptosis of squamous epithelium
Atrophy of squamous epithelium
Columnar epithelial metaplasia
Hyperplasia of columnar epithelium
