Who is at fault if driver A spins out on freeway in heavy rainstorm and a speeding driver B loses control to avoid A and collides with Driver C?

Based on my experience investigating traffic collisions in Ca. I'd make the following conclusion based on the limited info provided; Driver A would not be At Fault. Driver C would not be at fault. Driver B would be at fault for traveling at a speed unsafe for conditions. Insurance companies will probably place percentages of fault amongst all the drivers, however, under the vehicle code, driver B would be the one who would get cited if the investigating officer felt it was warranted.