2, 3 -dimethyl- 2 -butene can be prepared by heating which of the following compounds with a strong acid?
A. (CH₃)₂C = CH−CH₂−CH₃.
B. (CH₃)₂CH−CH₂(CH₃)−CH = CH₂
C. (CH₃)₃C−CH = CH₂
D. (CH₃)₂CH−CH₂-CH = CH₂