19. What do we learn from the passage about the air in Southern California? (D)
A、Itisunlikelytoimproveinthenearfuture.
B、Itisfreeofpollutionfromvehiclesandindustry.
C、Itisasdirtyasitwasbefore.
D、Itiscleanerthanitwasintheearly1990s.
发布时间：2025-05-14 05:05:24
