T=6π
∴ω=1/3
当x=π/2时,y=2
∴sin(1/3×π/2+φ)=1
即π/6+φ=2kπ+π/2
∴φ=2kπ+π/3
∵-π<φ≤π
∴φ=π/3
∴f(x)=2sin(x/3+π/3)
2kπ-π/2≤x/3+π/3≤2kπ+π/2 ↑
即6kπ-5π/2≤x≤6kπ+π/2(k∈Z)↑
2kπ+π/2≤x/3+π/3≤2kπ+3π/2 ↓
即6kπ+π/2≤x≤6kπ+7π/2(k∈Z)↓
∴选A