Select all of the following which represent a standard formation reaction.

K(s) + 1/2 Cl2(g) -> KCl(s)
2 C2H6(g) + 7 O2(g) -> 4 CO2(g) + 6 H2O(g)
1/2 H2(g) + 1/2 N2(g) + O2(g) -> HNO
A) 1 and 2
B) 1 and 3
C) 2 and 3
D) 1, 2, and 3