13. If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering? (A) 16 hours light/8 hours dark (B) 14 hours light/10 hours dark (C) 4 hours light/8 hours dark/4 hours light/8 hours dark (D) 8 hours light/8 hours dark/light flash/8 hours dark (E) all of above are flowering