Ludwig's angina usually begins in which of the following space?
Ludwig's angina is an acute, potentially life threatening, toxic cellulitis, beginning usually in the submandibular space and secondarily involving the sublingual and submental spaces as well. The disease is not usually considered to be true Ludwig’s angina unless all submandibular spaces are involved. 
Ref: Shafer's textbook of oral pathology 7th edition page 510
Submandibular space
Sublingual space
Submental space
All of the above