Answer:
D. All conditions for inference are met.
Explanation:
For the 10% condition :
x / n ; x = number of defective samples ; n = sample size
For Plant A :
x / n = 12 / 80 = 0.15 (> 0.10)
Plant B:
x / n = 10 / 90 = 0.11 (> 0.10)
The sample sizes are large enough ; n > 30
The questions stated that samples were chosen at random.
Hence, all conditions for inference are met.