The products are dinitrogen monoxide (N2O, also known as nitrous oxide or laughing gas) and water (H2O).
To verify, check that the equation is balanced:
N: 2 on each side (1 from NH4+ and 1 from NO3- on the left; 2 in N2O on the right).
H: 4 on each side (4 in NH4+ on the left; 4 in 2H2O on the right).
O: 3 on each side (3 in NO3- on the left; 1 in N2O + 2 in 2H2O on the right).
The other options are incorrect: NO2 and H2O would not balance correctly with the given reactant; N2O and O2 would leave hydrogen unaccounted for; and NO3 is not a stable molecular product of thermal decomposition.