#"(b) a redox reaction"#
#"(c) a comproportionation reaction"#.
#(aq)# simply means the #"aquated ion"#, or the ionic species in aqueous solution. For #Cu(SO_4)(aq)# this means #Cu^(2+)# and #SO_4^(2-)#, where in aqueous solution #Cu^(2+)# exists as the coordination complex #[Cu(OH_2)_6]^(2+)#, which has a truly beautiful blue colour.
In #"(c)"#, this is a subset of redox reaction, but here, instead of one species being reduced, and another species oxidized, which conventionally occurs, as for #"(b)"#, here the reactants are in different oxidations states, i.e. #N^(-III)# in #"ammonia"#, and #N^(+I)# in #"dinitrogen monoxide"# (note that we could formally assign oxidation states of #N^0#, and #N^(+II)# but the average oxidation is #N^(+I)#), these formally exchange electrons so that their product gives #N^(+I)#, a formal comproportionation.
I assume you are a first/second year undergrad. If you are an A-level student you don't need to know about #"comproportionation"#.
