How many of the following compounds will form acetic acid on reaction with hot concentrated 
 $KMn{O}_4/O{H}^{-}/\Delta$
i)  Prop-1-ene           ii) 2-methyl- 2- butene          iii) 2- methyl propene
iv) But-2-ene             v) cyclohexene                     vi) 1-butene