Distinguish which among the following chemical reactions is (are) combustion reaction(s):

a) 25= + <= → 25=<

b) 2!054<Q → !0=4<Q + 4<= + 5=<

c) 24U=5=p + 37<= → 24 4<= + 26 5=<

d) 4Q5p< + 4<= → 34<= + 35=<