For the radical chain reaction below, the correct classification for step 2 and step 3 is, respectively,
Step 1: \( \text{Br}_2 + M \longrightarrow 2 \text{Br}^+ + M \)
Step 2: \( \text{Br}^+ + \text{H}_2 \longleftrightarrow \text{HBr} + \text{H}^+ \)
Step 3: \( \text{H}^+ + \text{Br}_2 \longrightarrow \text{HBr} + \text{Br}^+ \)