[单选题]
Cracking is a process by which gaseous 1j -o*ntj e3c.f,o ymkalkanes are converted to smaller-chain alc*ef-n.k,jy1to j m3ovvw e)y ny,9(tkan,n) 9(vyetyw ves and alkenes. One possible reaction in the cracking of butane is shown.
What is the enthalpy change of the cracking reaction?
A. +80kJ mol$^{-1}$
B. +150kJ mol$^{-1}$
C. -80kJ mol$^{-1}$
D. -150kJ mol$^{-1}$