The heats of combustion (exothermic) for the four $C_6{H}_{12}$ isomers shown are (not necessarily in order) $955.3, 953.6, 950.6 and 949.7$(all in kilocalories per mole).  Which of these values in most likely the heat of combustion of isomer 1?
  

Larger the stability, smaller the heat of combustion.  More substituted alkenes are more stable. trans is more stable than cis.
Stability of isomer $2 > 3 > 1 > 4$
Thus, heat of combustion of isomers.
$$\begin{gathered} 4=-955.3kcalmo{l}^{-1} \\ 1=-953.6kcalmo{l}^{-1} \\ 3=-950.6kcalmo{l}^{-1} \\ 2=-949.7kcalmo{l}^{-1} \end{gathered}$$