A 60 -year-female patient presents with 4 -week history of a painless ulcer on the left lateral border of her tongue. she is a chronic cigarette smoke since her youth. clinical examination shows the ulcer has evereted margins and there is reduced mobility of her tongue. which one of the following the most likely diagnosis?
a. Submucous fibrosis
b. Erosive lichen planus
C. Leukoplakia
d. Erytherplakia
e. Squamous cell carcinoma