2,3-dimethyl-2-butene can be prepared by heating which of the following compounds with a strong acid?

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1. **Reaction Type:** Heating an alkene or alcohol with a strong acid (like $H_2SO_4$) typically leads to the formation of a more substituted alkene via the formation of a **carbocation intermediate** and subsequent rearrangement.
2. **Analysis of Option 2 ((CH3)3C-CH=CH2):** This compound is **3,3-dimethylbut-1-ene**.
   - **Protonation:** The acid protonates the double bond to form a secondary carbocation: $(CH_3)_3C-CH^+-CH_3$.
   - **Rearrangement:** A **1,2-methyl shift** occurs to form a more stable **tertiary carbocation**: $(CH_3)_2C^+-CH(CH_3)_2$.
   - **Elimination:** Elimination of a proton from the adjacent carbon yields the most substituted, stable alkene (Saytzeff product): **2,3-dimethylbut-2-ene** $((CH_3)_2C=C(CH_3)_2)$.
3. **Conclusion:** The rearrangement of the carbon skeleton in 3,3-dimethylbut-1-ene under acidic conditions leads directly to the formation of 2,3-dimethyl-2-butene.

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